SCRIPTING DOCUMENTATION
Version: 1.13.0.1

This is documentation for a beta release of Minecraft. New features, components, and capabilities in this release are not final and might change without notice before the final release.
Be sure to check the documentation once the release is out of beta if your add-on isn't working properly. Resource and Behavior Packs created for the beta are not guaranteed to work on the final release.

Index#

Scripting System#

The Minecraft Script Engine uses the JavaScript language.
You can write JavaScript scripts and bundle them with Behavior Packs to listen and respond to game events, get and modify data in components that entities have, and affect different parts of the game.

Demos#

Here are some demos from your friends at Minecraft to help you get started with scripting. Simply unzip them to check out the code, or import them as a .mcpack to play with them

Demo	Last Updated	Download Link
Turn-Based RPG	10/24/2018	https://aka.ms/minecraftscripting_turnbased
Mob Arena	10/24/2018	https://aka.ms/minecraftscripting_mobarena

Known Issues#

This is the list of currently known issues with the Minecraft Script Engine

Issue	Workaround
Scripts are not loaded properly from archived packs	Unzip script packs before applying them to a world. If you import a script pack with the .mcpack extension, it will unzip it for you
Custom UI doesn't work in VR or MR mode	Currently you will only be able to use custom UI when running the game in regular mode
Custom UI doesn't retain state upon suspend and resume	Currently there's no workaround for this issue
Exiting a world without scripts and entering one that has scripts might cause the wrong world to load	Restart Minecraft before loading a new world with scripts
Calling removeEntity on a dying entity might cause the game to crash	Don't call removeEntity the same frame you reduced the entity's damage to 0. Removing the entity forces it to be removed right away. Instead, save any dying entities and clean the up on the next frame (See the Turn-Based Demo for an example of this)

Breaking Changes#

While we continue to work and refine the experimental Scripting API we might need to make changes that will break your current scripts. Please check this section if your scripts aren't working as expected.

Category	Change
UI	engine.on now takes a facet name. In order to check for the script engine starting and connect it to the UI you will need the following: engine.on("facet:updated:core.scripting", ...); Followed by the following line after you are done doing your initialization: engine.trigger("facet:request", ["core.scripting"]);
Components	Calls to getComponent now return the component's parameters inside of the 'data' parameter of the return object.
Events	Event data objects now hold the event's parameters inside of the 'data' parameter of the event data object.
Events	Custom events need to be registered before using. Check the documentation for registerEventData for more information.
Events	Custom events need to have a namespace and can't use the 'minecraft' namespace. This namespace is reserved for built-in events only.
Events	Event Data is now standardized. Call createEventData to create an event data object prefilled with all the fields and default values for an event. You will need this event data object to trigger any events.

Pre-Requisites#

So you want to make your own Scripts? That's awesome! In this section you will find the list of minimum and recommended software you will need.
NOTE: Scripts are only supported on Windows 10 PCs at the moment. If you try to open a world with scripts on a device that doesn't support scripts, you will see an error message letting you know you can't enter the world.

Software	Minimum	Recommended
Minecraft	Minecraft on your Windows 10 device	Minecraft on your Windows 10 device
Code Editor	Visual Studio Code or any plain-text editor	Visual Studio Community 2017 with the following components installed: 'JavaScript diagnostics', 'JavaScript and TypeScript language support', 'Just-In-Time debugger'
Debugger	N/A	Visual Studio Community 2017
Other	Vanilla Behavior Pack available from https://aka.ms/behaviorpacktemplate	Vanilla Behavior Pack available from https://aka.ms/behaviorpacktemplate
Storage	1.0 GB of free space for text editor, game, and scripts	3.0 GB of free space for Visual Studio, game, and scripts

Getting Started#

First you will need to download the latest Vanilla Behavior Pack. You can get this from the following link: https://aka.ms/behaviorpacktemplate
Once you have downloaded the Behavior Pack, unzip it to a folder. Inside the Behavior Pack you will find the scripts folder which contains all the scripting files you want to run.
In the scripts folder you will find two folders: one for client scripts and one for server scripts.
-Server Scripts: These scripts run on the server side of the game. This includes spawning new entities, adding components, or modifying components on an entity.
-Client Scripts: These scripts run on each individual player's side of the game. This is a good place to respond to events and manage anything specific to the player.
Once you have chosen whether you are making a client or server script, simply add a new blank text file with .js extension to the appropriate folder, and open it in your preferred code editor. Then code away! You can have as many or as few JavaScript files as you want here (the name of the files doesn't matter) and they will all be run independently of each other!

NOTE: For scripts to be run by the game, you need to enable Experimental Gameplay on the world where you will run scripts on. This will be necessary while scripting is still in beta.
When entering a world that has client scripts in it, you will be prompted to accept that you wish to run scripts on your device (this will show up both for local worlds as well as multiplayer worlds).
Additionally, if your pack contains client scripts, you need to include a client_data module in the pack's manifest. This tells the game anything in the scripts/client folder needs to be sent over to the clients. Please refer to the Add-on Documentation page for more information on the pack's manifest contents.

Folder Structure

Example of manifest module needed for client scripts

        {
            "description": "Example client scripts module",
            "type": "client_data",
            "uuid": "c05a992e-482a-455f-898c-58bbb4975e47",
            "version": [0, 0, 1]
        }

vanilla_behavior_pack

|-scripts
|--client
|---myClientScript.js
|--server
|---myServerScript.js
|-manifest.json
|-pack_icon.png

Structure of a Script#

In this section you can find a quick description of the basic structure of a JavaScript script file for the Minecraft Script Engine. If you would like to learn more about JavaScript or want to follow a fundamentals tutorial, you can check the official documentation on the Mozilla Developer Network here: https://developer.mozilla.org/docs/Web/JavaScript
These are, in a way, the required parts of a script but they are by no means the only parts you can have. You can create additional methods as needed - just make sure they are called from somewhere in one of the methods below!

1. System Registration#

First off we need to register the system for our file. This signs up our script to be set-up either on the client or server threads of the game. Generally speaking, you will choose based on whether you put the script file in the client or server folders. To do that simply call registerSystem on either the client or server and give it the version of the API you require.

Parameters

Name	Type	Description
majorVersion	Integer	This is the major version of the Minecraft Script Engine your script was designed to work with
minorVersion	Integer	This is the revision of the Minecraft Script Engine your script was designed to work with

Code Examples:

Client System

let sampleClientSystem = client.registerSystem(0, 0);

Server System

let sampleServerSystem = server.registerSystem(0, 0);

2. System Initialization#

This is the first method that gets called immediately after the system is registered. It will run as soon as the script loads at world start.
You can use this to set up the environment for your script: register custom components and events, sign up event listeners, etc. This will run BEFORE the world is ready and the player has been added to it. This function should be used to initialize variables and setup event listeners. You shouldn't try to spawn or interact with any entities at this point! You should also avoid interaction with UI elements or sending messages to the chat window since this is called before the player is ready.

Code Example:

sampleSystem.initialize = function() {
  //register event data, register components, register queries, listen for events
};

3. System Update#

This method gets called once every game tick. The server and client tick at 20 times per second. This is a good place to get, check, and react to component changes.

Code Example:

sampleSystem.update = function() {
  //Update all the things
};

4. System Shutdown#

This method gets called when the Minecraft Script Engine is shutting down. For the client this is when they leave the world; for the server this is after the last player has exited the world.

Code Example:

sampleSystem.shutdown = function() {
  //Cleanup script only things
};

Debugging#

Your script isn't working or doing what you want it to do? Fret not! We have built some debugging capabilities into the Script Engine to help you figure out what's going on with your script. If you are new to programming or want to learn more about debugging we suggest checking out the documentation about debugging with Visual Studio available here: https://docs.microsoft.com/visualstudio/debugger

There are two ways to tell what happened when something goes wrong with a script: in-game and advanced, which we will describe below. You only need the game and your script to debug in-game, but you will need a Windows 10 PC and Visual Studio installed for the advanced debugging.

In-Game#

When you run a script in the game, the Script Engine will print out error messages whenever something goes wrong. For example, if you try to get a component that the script engine doesn't know about you will get an error.
To look at these messages you can open the chat screen which will have all the generated error messages there; or you can open the log file that the game generated. The location of the log file varies by platform. On Windows 10 you can find the log file in ' %APPDATA%\..\Local\Packages\Microsoft.MinecraftUWP_8wekyb3d8bbwe\LocalState\logs '
We strongly encourage you to build further debug messages and tools into your scripts while working on them. This will help you discern when something isn't working quite right. Reach out on the official Discord channel if you need additional help: https://discord.gg/Minecraft

Real-Time (Advanced)#

If you have a Windows 10 PC with Visual Studio installed, you can attach the Visual Studio debugger and debug your script in real-time.
If you installed Visual Studio with the components mentioned in the "Recommended" section of this document you will have installed and enabled the Just-In-Time Debugger. This tool will pop-up a message from Visual Studio whenever an exception occurs in your script and allow you to open Visual Studio on the line of your script that broke.

Additionally, you can connect to the Script Engine manually and debug your code. You can use remote debugging to connect and debug Minecraft running on another device. Please refer to the Visual Studio Debugger documentation above for instructions on how to use remote debugging.
First you need to start up Visual Studio. If this is the first time you have launched Visual Studio after installation, we suggest setting up your environment for JavaScript development and logging in to your Microsoft account when prompted. This will set up the Visual Studio interface with the most important tools you will need.
Once you have Visual Studio open you should launch Minecraft. Then create a new world with Experimental Gameplay enabled and apply the Behavior Pack containing your scripts.
After creating the world go back to Visual Studio and click on the Debug menu. Then click on "Attach to Process". In the window that opens there will be a search box titled Filter Process. Click on it and type Minecraft.
Once the list is narrowed down to only the instance of Minecraft running, you can verify that the Script Engine is running by looking at the Type column. This will say Script and either x86 or x64.

Select the process and click on Attach to attach the debugger to the game. Now you will be able to press the Pause button to pause the Script Engine when the next line of script code runs. This allows you to inspect the values of variables in your script and break into Visual Studio if an error occurs in your code.
WARNING: When you hit a breakpoint to step through code with a debugger, it is possible for a client to time out and disconnect or for the server to disconnect all players.

Script API Objects#

Here you can find the definition of some objects returned by the script API.

Entity JS API Object#

Name	Type	Entity JS API Object	Description
__type__	String		READ ONLY. This defines the type of object. Can be: "entity" or "item_entity".
__identifier__	String		READ ONLY. This is the identifier for the object in the format namespace:name. For example, if the type is entity and the object is representing a vanilla cow, the identifier would be minecraft:cow
id	Positive Integer		READ ONLY. This is the unique identifier of the entity.

Level JS API Object#

Name	Type	Level JS API Object	Description
__type__	String		READ ONLY. This defines the type of object. Will be: "level".
level_id	Positive Integer		READ ONLY. This is the unique identifier of the level.

Component JS API Object#

Name	Type	Component JS API Object	Description
__type__	String		READ ONLY. This defines the type of object. Will be: "component".
data	JavaScript Object		This is the content of the component.

Query JS API Object#

Name	Type	Query JS API Object	Description
__type__	String		READ ONLY. This defines the type of object. Will be: "query".
query_id	Positive Integer		READ ONLY. This is the unique identifier of the query.

ItemStack JS API Object#

Name	Type	ItemStack JS API Object	Description
__type__	String		READ ONLY. This defines the type of object. Will be: "item_stack".
__identifier__	String		READ ONLY. This is the identifier for the object in the format namespace:name. For example, if the type is entity and the object is representing a vanilla cow, the identifier would be minecraft:cow
item	String		READ ONLY. This is the identifier of the item.
count	String		READ ONLY. This is the number of items in the stack.

Block JS API Object#

Name	Type	Block JS API Object	Description
__type__	String		READ ONLY. This defines the type of object. Will be: "block".
__identifier__	String		READ ONLY. This is the identifier for the object in the format namespace:name. For example, if the type is block and the object is representing a block of bedrock, the identifier would be minecraft:bedrock
ticking_area	JavaScript Object		READ ONLY. This is the ticking area object that was used to get this block.
block_position	JavaScript Object		READ ONLY. This is the position of the block and it functions as part of its unique identifier. Parameters# Name Type Description x Integer The x position y Integer The y position z Integer The z position

Ticking Area JS API Object#

There are two types of ticking area objects. Entity and Level. When a function calls for a ticking area it can take either type as an argument.

Entity Ticking Area JS API Object#

Name	Type	Entity Ticking Area JS API Object	Description
__type__	String		READ ONLY. This defines the type of object. Will be: "entity_ticking_area".
entity_ticking_area_id	Positive Integer		READ ONLY. This is the unique identifier of the ticking area.

Level Ticking Area JS API Object#

Name	Type	Level Ticking Area JS API Object	Description
__type__	String		READ ONLY. This defines the type of object. Will be: "level_ticking_area".
level_ticking_area_id	String		READ ONLY. This is the unique identifier of the ticking area.

Script Bindings#

Bindings are the capabilities of the Minecraft Script Engine to change or modify things in the game.

Logging Bindings#

log(Message)#

The log function is accessed through the server or client objects and allows for logging a message to the ContentLog file. On Windows 10 devices it is located at ' %APPDATA%\..\Local\Packages\Microsoft.MinecraftUWP_8wekyb3d8bbwe\LocalState\logs '

Parameters#

Name	Type	Description
Message	String	The message that you want to send to the log file

Code Example:

Log

system.exampleFunction = function() {
  client.log("example log message") 
}; 

Entity Bindings#

createEntity()#

Creates an empty entity with no components and does not place it in the world. The empty entity will be of type custom and have a blank identifier. This is NOT a valid entity that exists in the world, just an empty one that only scripts know about.

NOTE: Entities are created first on the server, with the client notified of new entities afterwards. Be aware that if you send the result object to the client right away, the created entity might not exist on the client yet.

Return Value#

Type	Value	Description
Entity JS API Object	object	An object representing the newly created entity
JavaScript Object	null	Something went wrong when creating the entity

createEntity(Type, TemplateIdentifier)#

Creates an entity and applies the specified template as defined in JSON. This allows you to quickly create an entity from the applied Behavior Packs as the base for an entity created in scripting. The entity will be spawned into the world with all the components, component groups, and event triggers that are defined in the JSON file of the identifier specified. Only works on scripts registered on the server.NOTE: Entities are created first on the server, with the client notified of new entities afterwards. Be aware that if you send the result object to the client right away, the created entity might not exist on the client yet.

Parameters#

Name	Type	Description
Type	String	Specifies the type of the entity that is being created by the template. Valid inputs are `entity` and `item_entity`
TemplateIdentifier	String	This can be any of the entity identifiers from the applied Behavior Packs. For example specifying minecraft:cow here will make the provided entity a cow as defined in JSON

Return Value#

Type	Value	Description
Entity JS API Object	object	An object representing the newly created entity
JavaScript Object	null	Something went wrong when creating the entity

destroyEntity(EntityObject)#

Destroys an entity identified by the EntityObject. If the entity exists in the world this will remove it from the world and destroy it. This also makes the EntityObject no longer valid - you should only destroy an entity after you are done with it and no longer need to reference it again. This does NOT kill the entity. There won't be an event for its death: it will be removed.

Parameters#

Name	Type	Description
EntityObject	Entity JS API Object	The object that was retrieved from a call to createEntity() or retrieved from an entity event

Return Value#

Type	Value	Description
Boolean	true	The entity was successfully destroyed
JavaScript Object	null	Something went wrong when destroying the entity

isValidEntity(EntityObject)#

Checks if the given EntityObject corresponds to a valid entity.

Parameters#

Name	Type	Description
EntityObject	Entity JS API Object	The object that was retrieved from a call to createEntity() or retrieved from an entity event

Return Value#

Type	Value	Description
Boolean	true	The entity is in the Script Engine's database of entities
Boolean	false	The entity is not in the Script Engine's database of entities
JavaScript Object	null	Something went wrong when validating the entity

Component Bindings#

registerComponent(ComponentIdentifier, ComponentData)#

Creates a custom component that only exists in script. It can be then added, removed, and updated from entities. These custom components only exist while the Script Engine is running.

Parameters#

Name	Type	Description
ComponentIdentifier	String	The identifier of the custom component. It is required to use a namespace so you can uniquely refer to it later without overlapping a name with a built-in component: for example 'myPack:myCustomComponent'
ComponentData	JavaScript Object	A JavaScript Object that defines the name of the fields and the data each field holds inside the component.

Return Value#

Type	Value	Description
Boolean	true	The component was successfully registered
JavaScript Object	null	Something went wrong when registering the component

Code Example:

Registering a custom component

const mySystem = server.registerSystem(0, 0);

mySystem.initialize = function() {
  this.registerComponent("myPack:myCustomComponent", { myString: "string", myNumber: 0, myBool: true, myArray: [1, 2, 3] });
};

createComponent(EntityObject, ComponentIdentifier)#

Creates the specified component and adds it to the entity. This should only be used with custom components which need to be registered first. If the entity already has the component, this will retrieve the component already there instead.

Parameters#

Name	Type	Description
EntityObject	Entity JS API Object	The EntityObject that was retrieved from a call to createEntity() or retrieved from an event
ComponentIdentifier	String	The identifier of the component to add to the entity. This is either the identifier of a built-in component (check the Script Components section) or a custom component created with a call to registerComponent()

Return Value#

Type	Value	Description
Component JS API Object	object	An object with the following fields, and additionally, all the fields as defined in the component
JavaScript Object	null	Something went wrong when creating the component

Code Example:

Creating a custom component

let globals = {
  ready: false
};

const mySystem = server.registerSystem(0, 0);

mySystem.initialize = function() {
  this.registerComponent("myPack:myCustomComponent", { myString: "string", myNumber: 0, myBool: true, myArray: [1, 2, 3] });
}

mySystem.update = function() {
  if(globals.ready == false) {
    globals.ready = true;
    let myEntity = this.createEntity();
    if(myEntity != null) {
      let myComponent = this.createComponent(myEntity, "myPack:myCustomComponent");
    }
  }
};

hasComponent(EntityObject, ComponentIdentifier)#

Checks if the given entity has the specified component.

Parameters#

Name	Type	Description
EntityObject	Entity JS API Object	The EntityObject that was retrieved from a call to createEntity() or retrieved from an event
ComponentIdentifier	String	The identifier of the component to check on the entity. This is either the identifier of a built-in component (check the Script Components section) or a custom component created with a call to registerComponent()

Return Value#

Type	Value	Description
Boolean	true	The EntityObject has the component
Boolean	false	The EntityObject doesn't have the component
JavaScript Object	null	An unknown component was passed in or something else went wrong when checking if the EntityObject had the component

Code Example:

Check whether an entity has specified component

let globals = {
  ready: false
};

const mySystem = server.registerSystem(0, 0);

mySystem.update = function() {
  if(globals.ready == false) {
    globals.ready = true;
    let entity = this.createEntity("entity", "minecraft:pig");
    if(this.hasComponent(entity, "minecraft:nameable")) {
      // Do some work
    }
  }
};

getComponent(EntityObject, ComponentIdentifier)#

Looks for the specified component in the entity. If it exists, retrieves the data from the component and returns it.

Parameters#

Name	Type	Description
EntityObject	Entity JS API Object	The EntityObject that was retrieved from a call to createEntity() or retrieved from an event
ComponentIdentifier	String	The identifier of the component to retrieve from the entity. This is either the identifier of a built-in component (check the Script Components section) or a custom component created with a call to registerComponent()

Return Value#

Type	Value	Description
Component JS API Object	object	An object with the following fields, and additionally, all the fields as defined in the component Component JS API Object# Name Type Component JS API Object Description __type__ String READ ONLY. This defines the type of object. Will be: "component". data JavaScript Object This is the content of the component.
JavaScript Object	null	The entity did not have the component or something went wrong when getting the component

Code Example:

Get a specified component from an entity

let globals = {
  ready: false
};

const mySystem = server.registerSystem(0, 0);

mySystem.update = function() {
  if(globals.ready == false) {
    globals.ready = true;
    let entity = this.createEntity("entity", "minecraft:pig");
    let positionComponent = this.getComponent(entity, "minecraft:position");
    if (positionComponent != null) {
      positionComponent.data.x = 0;
      positionComponent.data.y = 0;
      positionComponent.data.z = 0;
    }
  }
};

applyComponentChanges(EntityObject, ComponentObject)#

Applies the component and any changes made to it in script back to the entity. What this means for each component can be slightly different: it makes the component reload on the entity with the new data as if it had just been added to the entity.

Parameters#

Name	Type	Description
EntityObject	Entity JS API Object	The entity object that we are applying the component changes to
ComponentObject	Component JS API Object	The component object retrieved from the entity that was returned by either createComponent() or getComponent()

Return Value#

Type	Value	Description
Boolean	true	The component was successfully updated
JavaScript Object	null	Something went wrong when updating the component

Code Example:

Apply updates to an entity's component

let globals = {
  pig: null
};

const mySystem = server.registerSystem(0, 0);

mySystem.update = function() {
  if(globals.pig == null) {
    globals.pig = this.createEntity("entity", "minecraft:pig");
  }
  else {
    let positionComponent = this.getComponent(globals.pig, "minecraft:position");
    positionComponent.data.y += 0.1;
    this.applyComponentChanges(globals.pig, positionComponent);
  }
};

destroyComponent(EntityObject, ComponentIdentifier)#

Removes the specified component from the given entity. If the entity has the component, it will be removed. Currently this only works with custom components and can't be used to remove components defined for an entity in JSON.

Parameters#

Name	Type	Description
EntityObject	Entity JS API Object	The EntityObject that was retrieved from a call to createEntity() or retrieved from an event
ComponentIdentifier	String	The identifier of the component to remove from the entity. This is either the identifier of a built-in component (check the Script Components section) or a custom component created with a call to registerComponent()

Return Value#

Type	Value	Description
Boolean	true	The component was successfully removed from the entity
JavaScript Object	null	The entity did not have the component or something went wrong when removing the component

Code Example:

Destroy an entity's component

let globals = {
  myEntity: null
};

const mySystem = server.registerSystem(0, 0);

mySystem.initialize = function() {
  this.registerComponent("myPack:myCustomComponent", { myString: "string", myNumber: 0, myBool: true, myArray: [1, 2, 3] });
};

mySystem.update = function() {
  if(globals.myEntity == null) {
    globals.myEntity = this.createEntity();
  }
  else {
    if(this.hasComponent(globals.myEntity, "myPack:myCustomComponent")) {
      this.destroyComponent(globals.myEntity, "myPack:myCustomComponent");
    }
    else {
      this.createComponent(globals.myEntity, "myPack:myCustomComponent");
    }
  }
};

Event Bindings#

These are the bindings used to handle events. For a list of events you can react to or trigger, check the Events section of this document.

registerEventData(EventIdentifier, EventData)#

Registers the Event to the script engine. This allows you to create Event Data by calling createEventData and have it initialized with the correct default data and fields. Only custom events need to be registered.

Parameters#

Name	Type	Description
EventIdentifier	String	This is the identifier of the custom event we are registering. The namespace is required and can't be set to minecraft.
EventData	JavaScript Object	The JavaScript object with the correct fields and default values for the event

Return Value#

Type	Value	Description
Boolean	true	Successfully registered the event data
JavaScript Object	null	Something went wrong when registering the event for listening

createEventData(EventIdentifier)#

Creates an object with all the required fields and default data for the specified event. If the event is a custom event, it needs to have been previously registered.

Parameters#

Name	Type	Description
EventIdentifier	String	This is the identifier of the custom event we are registering. The namespace is required and can't be set to minecraft.

Return Value#

Type	Value	Description
JavaScript Object		The object containing the event data
JavaScript Object	null	Something went wrong when registering the event for listening

listenForEvent(EventIdentifier, CallbackObject)#

Allows you to register a JavaScript object that gets called whenever the specified event is broadcast. The event can either be a built-in event or an event specified in script.

Parameters#

Name	Type	Description
EventIdentifier	String	This is the identifier of the event to which we want to react. Can be the identifier of a built-in event or a custom one from script
CallbackObject	JavaScript Object	The JavaScript object that will get called whenever the event is broadcast

Return Value#

Type	Value	Description
Boolean	true	Successfully registered to listen for the event
JavaScript Object	null	Something went wrong when registering the event for listening

Code Example:

Register a callback for a specified event

const mySystem = client.registerSystem(0, 0);

mySystem.initialize = function() {
  this.listenForEvent("minecraft:client_entered_world", (eventData) => this.onClientEnteredWorld(eventData));
};

mySystem.onClientEnteredWorld = function(eventData) {
  let messageData = this.createEventData("minecraft:display_chat_event");
  messageData.data.message = "Player has entered the world";
  this.broadcastEvent("minecraft:display_chat_event", messageData);
};

broadcastEvent(EventIdentifier, EventData)#

Allows you to trigger an event with the desired data from script. Anything that signed up to listen for the event will be notified and the given data delivered to them.

Parameters#

Name	Type	Description
EventIdentifier	String	This is the identifier of the event we want to react to. Can be the identifier of a built-in event or a custom one from script
EventData	JavaScript Object	The data for the event. You can create a new JavaScript Object with the parameters you want to pass in to the listener and the engine will take care of delivering the data to them

Return Value#

Type	Value	Description
Boolean	true	Successfully broadcasted the event
JavaScript Object	null	Something went wrong when broadcasting the event

Code Example:

Broadcasting an event

const mySystem = client.registerSystem(0, 0);

mySystem.initialize = function() {
  let eventData = this.createEventData("minecraft:display_chat_event");
  eventData.data.message = "Hello, World!";
  this.broadcastEvent("minecraft:display_chat_event", eventData);
};

Entity Queries#

Entity Queries are a way for you to filter for entities based on their components. Once you have registered a query, you can request all the entities that are captured by it. Entity Queries will only ever return entities that are currently active in the level. If your query extends into chunks that are not currently loaded, entities there will not be included in the query.

registerQuery()#

Allows you to register a query. A query will contain all entities that meet the filter requirement.
No filters are added by default when you register a query so it will capture all entities.

Return Value#

Type	Value	Description
Query JS API Object	object	An object containing the ID of the query
JavaScript Object	null	Something went wrong when creating the query

Code Example:

Query Registration

const mySystem = server.registerSystem(0, 0);

mySystem.initialize = function() {
  let myQuery = this.registerQuery();
};

registerQuery(Component, ComponentField1, ComponentField2, ComponentField3)#

Allows you to register a query that will only show entities that have the given component and define which fields of that component will be used as a filter when getting the entities from the query. You can either provide just the component identifier, or the component identifier and the name of 3 properties on that component to be tested (If you do specify property names, you must specify 3).

Parameters#

Name	Type	Default Value	Description
Component	String		This is the identifier of the component that will be used to filter entities when
ComponentField1	String	"x"	This is the name of the first field of the component that we want to filter entities by. By default this is set to x.
ComponentField2	String	"y"	This is the name of the second field of the component that we want to filter entities by. By default this is set to y.
ComponentField3	String	"z"	This is the name of the third field of the component that we want to filter entities by. By default this is set to z.

Return Value#

Type	Value	Description
Query JS API Object	object	An object containing the ID of the query
JavaScript Object	null	Something went wrong when creating the query

Code Example:

Query Registration

const mySystem = server.registerSystem(0, 0);

mySystem.initialize = function() {
  let spatialQuery = this.registerQuery("minecraft:position", "x", "y", "z");
};

addFilterToQuery(Query, ComponentIdentifier)#

By default no filters are added. This will allow queries to capture all entities.

Parameters

Name	Type	Description
Query	Query JS API Object	The object containing the ID of the query that you want to apply the filter to
ComponentIdentifier	String	This is the identifier of the component that will be added to the filter list. Only entities that have that component will be listed in the query

Code Example:

Adding a filter to a query

let globals = {
  simpleQuery: null
};
const mySystem = server.registerSystem(0, 0);

mySystem.initialize = function() {
  globals.simpleQuery = this.registerQuery();
};

mySystem.update = function() {
  globals.simpleQuery = this.registerQuery();
  this.addFilterToQuery(globals.simpleQuery, "minecraft:explode");  let explodingEntities = this.getEntitiesFromQuery(globals.simpleQuery);
  for(var entity in explodingEntities) {
    server.log(JSON.stringify(entity));
  }
};

getEntitiesFromQuery(Query)#

Allows you to fetch the entities captured by a query.

Parameters#

Name	Type	Description
Query	Query JS API Object	This is the query you registered earlier using registerQuery()

Return Value#

Type	Value	Description
Array	array	An array of EntityObjects representing the entities found within the query
JavaScript Object	null	Something went wrong when creating the entity

Code Example:

Get a list of entities from a query

const mySystem = server.registerSystem(0, 0);

mySystem.update = function() {
  let simpleQuery = this.registerQuery();
  let allEntities = this.getEntitiesFromQuery(simpleQuery);
  for(var entity in allEntities) {
    server.log(JSON.stringify(entity));
  }
};

getEntitiesFromQuery(Query, ComponentField1_Min, ComponentField2_Min, ComponentField3_Min, ComponentField1_Max, ComponentField2_Max, ComponentField3_Max)#

Allows you to fetch the entities captured by a query that was created with a component filter built-in. The only entities that will be returned are those entities that have the component that was defined when the query was registered and that have a value in the three fields on that component that were defined in the query within the values specified in the call to getEntitiesFromQuery.

Parameters#

Name	Type	Description
Query	Query JS API Object	This is the query you created earlier using registerQuery(...)
ComponentField1_Min	Decimal	The minimum value that the first component field needs to be on an entity for that entity to be included in the query
ComponentField2_Min	Decimal	The minimum value that the second component field needs to be on an entity for that entity to be included in the query
ComponentField3_Min	Decimal	The minimum value that the third component field needs to be on an entity for that entity to be included in the query
ComponentField1_Max	Decimal	The maximum value that the first component field needs to be on an entity for that entity to be included in the query
ComponentField2_Max	Decimal	The maximum value that the second component field needs to be on an entity for that entity to be included in the query
ComponentField3_Max	Decimal	The maximum value that the third component field needs to be on an entity for that entity to be included in the query

Return Value#

Type	Value	Description
Array	array	An array of EntityObjects representing the entities found within the query
JavaScript Object	null	Something went wrong when creating the entity

Code Example:

Get a list of entities from a query

let globals = {
  spatialQuery: null
};

const mySystem = server.registerSystem(0, 0);

mySystem.initialize = function() {
  globals.spatialQuery = this.registerQuery("minecraft:position", "x", "y", "z");
};

mySystem.update = function() {
  let closeEntities = this.getEntitiesFromQuery(globals.spatialQuery, 0, 10, 0, 5, 0, 10);
  for(var entity in closeEntities) {
    server.log(JSON.stringify(entity));
  }
};

Slash Commands#

You can use the traditional Slash Command system from scripts. Currently you can either trigger an event ("minecraft:execute_command") or use the executeCommand binding. Commands in scripts are restricted to server scripts, they can't be run from the client's side at the moment.

executeCommand(Command, Callback)#

Allows you to execute a Slash Command on the server. The command will be queried and executed at the end of the current frame. All data output from the command will be compiled on a JavaScript Object and sent to the Callback object specified in the second parameter.

Parameters

Name	Type	Description
Command	String	The slash command to run
Callback	JSON Object	The JavaScript object that will be called after the command executes

Example

system.executeCommand("/fill ~ ~ ~ ~100 ~5 ~50 stone", (commandResultData) => this.commandCallback(commandResultData));

system.commandCallback = function (commandResultData) {
  let eventData = this.createEventData("minecraft:display_chat_event");
  if (eventData) {
    eventData.data.message = message;
    this.broadcastEvent("minecraft:display_chat_event", "Callback called! Command: " + commandResultData.command + " Data: " + JSON.stringify(commandResultData.data, null, "    ") );
  }
};

Block Bindings#

These functions define how you interact with blocks.

getBlock(Ticking Area, x, y, z)#

Allows you to get a block from the world when provided an x, y, and z position. The block must be within a ticking area.

Parameters#

Name	Type	Description
Ticking Area	Ticking Area JS API Object	The ticking area the block is in
x	Integer	The x position of the block you want
y	Integer	The y position of the block you want
z	Integer	The z position of the block you want

Return Value#

Type	Value	Description
Block JS API Object	object	An object containing the block
JavaScript Object	null	Something went wrong when retrieving the block

getBlock(Ticking Area, PositionObject)#

Allows you to get a block from the world when provided a JavaScript object containing a position. The block must be within a ticking area.

Parameters#

Name	Type	Description
Ticking Area	Ticking Area JS API Object	The ticking area the block is in
PositionObject	JavaScript Object	A JavaScript object with the x, y, and z position of the block you want Parameters# Name Type Description x Integer The x position y Integer The y position z Integer The z position

Return Value#

Type	Value	Description
Block JS API Object	object	An object containing the block
JavaScript Object	null	Something went wrong when retrieving the block

getBlocks(Ticking Area, x min, y min, z min, x max, y max, z max)#

Allows you to get an array of blocks from the world when provided a minimum and maximum x, y, and z position. The blocks must be within a ticking area.

Parameters#

Name	Type	Description
Ticking Area	Ticking Area JS API Object	The ticking area the blocks are in
x min	Integer	The minimum x position of the blocks you want
y min	Integer	The minimum y position of the blocks you want
z min	Integer	The minimum z position of the blocks you want
x max	Integer	The maximum x position of the blocks you want
y max	Integer	The maximum y position of the blocks you want
z max	Integer	The maximum z position of the blocks you want

Return Value#

Type	Value	Description
Array	array	A 3D array of block objects. Indexs are the blocks positions relative to the min position given
JavaScript Object	null	Something went wrong when retrieving the blocks

getBlocks(Ticking Area, Minimum PositionObject, Maximum PositionObject)#

Allows you to get an array of blocks from the world when provided a minimum and maximum position. The blocks must be within a ticking area.

Parameters#

Name	Type	Description
Ticking Area	Ticking Area JS API Object	The ticking area the blocks are in
Minimum PositionObject	JavaScript Object	A JavaScript object with the minimum x, y, and z position of the blocks you want Parameters# Name Type Description x Integer The x position y Integer The y position z Integer The z position
Maximum PositionObject	JavaScript Object	A JavaScript object with the maximum x, y, and z position of the blocks you want Parameters# Name Type Description x Integer The x position y Integer The y position z Integer The z position

Return Value#

Type	Value	Description
Array	array	A 3D array of block objects. Indexs are the blocks positions relative to the min position given
JavaScript Object	null	Something went wrong when retrieving the blocks

Script Components#

This is the documentation for the attributes, properties, and components available from the Minecraft Script Engine.
There are two kinds of components: server components and client components. We will go into a bit more detail on what they are in their respective sections below.
Components can be added, retrieved, updated, and removed from entities. They do not exist on their own. Currently only user-defined components can be added and removed from entities. A component must be in an entity in order to retrieve or update it.
Check the Script Engine Bindings section to see how to add, remove, retrieve, and update components. This section deals with the specific API of each component.

Level Components#

These are the components that belong to the level. They can only belong on the level object and cannot be removed from it. You can get the components and change their data through the global server object.

let levelComponent = this.getComponent(server.level, "minecraft:example_level_component");

minecraft:ticking_areas#

This component gives access to the static ticking areas in the level. The component contains an array of ticking areas. The ticking areas can be accessed by name or by UUID if they were not given a name.

minecraft:weather#

The weather component allows users to change the level's weather. Rain and lightning levels can be changed independently and the default weather cycle can be turned off completely.

Parameters

Name	Type	Description
do_weather_cycle	Boolean	This is the world option that determines if the vanilla weather cycle will be used
rain_level	Decimal	A value between 0 and 1 that determains how heavy the rainfall is
rain_time	Integer	How long, in ticks, it will rain for
lightning_level	Decimal	A value between 0 and 1 that determines how much lightning and thunder there is
lightning_time	Integer	How long, in ticks, it will lightning and thunder for

Server Components#

These are the components that run on the server and are synced with all the clients (players) in the world.
As much as possible, the API of each component matches its JSON counterpart (with some differences noted).

minecraft:armor_container#

This component represents the armor contents of an entity. The component contains an array of ItemStack JS API Objects representing each slot in the armor container. NOTE: Currently items and containers are read-only. Slots are ordered from head to feet.

// This example will check the players helmet armor slot for a specific item after the player attacks an entity.
system.listenForEvent("minecraft:player_attacked_entity", function(eventData) {
    // Get the players armor container
    let playerArmor = system.getComponent(eventData.data.player, "minecraft:armor_container");
    // Get the players helmet
    let playerHelmet = playerArmor.data[0];
    // Destroy the attacked entity if the player has a gold helmet equipped
    if (playerHelmet.item == "minecraft:golden_helmet") {
        system.destroyEntity(eventData.data.attacked_entity);
    }
});

minecraft:attack#

This component controls the Attack Damage attribute from the entity. It allows you to change the current minimum and maximum values. Once the changes are applied, the current attack of the entity will be reset to the minimum specified. With the minimum and maximum changed to the values specified. Any buffs or debuffs will be left intact.

Parameters

Name	Type	Default Value	Description
damage	Range [a, b]		Range of the random amount of damage the melee attack deals. A negative value can heal the entity instead of hurting it Name Type Default Value Description range_min Decimal 0.0 The minimum amount of damage the entity will deal range_max Decimal 0.0 The maximum amount of damage the entity will deal

minecraft:container#

This component represents the container of a block. The component contains an array of ItemStack JS API Objects representing each slot in the container. This specific component is used for blocks. Refer to inventory components for entities. NOTE: Currently items and containers are read-only. Slots are ordered left to right.

// This example will check if a block has a container.
let block; // check getBlock API on how to access a block
let has_container = system.hasComponent(block, "minecraft:container");
if (has_container === true) {
  let container = system.getComponent(block, "minecraft:container");
  // you can now use the container to read items.

minecraft:collision_box#

Controls the collision box of the entity. When changes to the component are applied the entity's collision box is immediately updated to reflect the new dimensions. WARNING: If the change of the collision box dimensions would cause the entity to be inside a block, the entity might become stuck there and start suffocating.

Parameters

Name	Type	Default Value	Description
width	Decimal	1.0	Width and Depth of the collision box in blocks. A negative value will be assumed to be 0
height	Decimal	1.0	Height of the collision box in blocks. A negative value will be assumed to be 0

minecraft:damage_sensor#

Defines an array of damages and how the entity reacts to them - including whether the entity ignores that damage or not. Currently Minecraft triggers can't be properly serialized so any existing triggers will be completely replaced when applyComponentChanges().

Parameters

Name	Type	Default Value	Description
triggers	Array		List of triggers with the events to call when taking specific kinds of damage. Name Type Default Value Description on_damage JSON Object Specifies filters for entity definitions and events. deals_damage Boolean true If true, the damage dealt to the entity will take away health from it, set to false to make the entity ignore that damage. cause String Type of damage that triggers this set of events. damage_multiplier Decimal 1.0 A multiplier that modifies the base damage from the damage cause. If deals_damage is true the multiplier can only reduce the damage the entity will take to a minimum of 1.

// This example will cause an entity (in this case, a creeper) to start exploding when the player attacks it.
// Note: the entity must have the damage_sensor component and the associated events defined in their JSON description.
this.listenForEvent("minecraft:player_attacked_entity", function(eventData) {
  let damageSensorComponent = serverSystem.getComponent(eventData.attacked_entity, "minecraft:damage_sensor");
  damageSensorComponent.data[0].on_damage = { event:"minecraft:start_exploding", filters:[{test:"has_component", operator:"==", value:"minecraft:breathable"}] };
  serverSystem.applyComponentChanges(eventData.attacked_entity, damageSensorComponent);
});

minecraft:equipment#

Defines the loot table the entity uses to defines its equipment. Once the changes are applied, the equipment is re-rolled and a new set of equipment is chosen for the entity.

Parameters

Name	Type	Default Value	Description
table	String		The file path to the equipment table, relative to the behavior pack's root
slot_drop_chance	List		A list of slots with the chance to drop an equipped item from that slot

minecraft:equippable#

Defines how many and what items the entity can be equipped with.

Parameters

slots#

List of slots and the item that can be equipped

Parameters

Name	Type	Default Value	Description
slot	Integer	0	The slot number of this slot
accepted_items	List		The list of items that can go in this slot
item	String		Identifier of the item that can be equipped for this slot
interact_text	String		Text to be displayed when the entity can be equipped with this item when playing with Touch-screen controls
on_equip	String		Event to trigger when this entity is equipped with this item
on_unequip	String		Event to trigger when this item is removed from this entity

minecraft:explode#

Controls the entity's explosion, timer until the explosion, and whether the timer is counting down or not.

Parameters

Name	Type	Default Value	Description
fuse_length	Range [a, b]	[0.0, 0.0]	The range for the random amount of time the fuse will be lit before exploding, a negative value means the explosion will be immediate
power	Decimal	3.0	The radius of the explosion in blocks and the amount of damage the explosion deals
max_Resistance	Decimal	Infinite	A blocks explosion resistance will be capped at this value when an explosion occurs
fuse_lit	Boolean	false	If true, the fuse is already lit when this component is added to the entity
causes_fire	Boolean	false	If true, blocks in the explosion radius will be set on fire
breaks_blocks	Boolean	true	If true, the explosion will destroy blocks in the explosion radius
fire_affected_by_griefing	Boolean	false	If true, whether the explosion causes fire is affected by the mob griefing game rule
destroy_affected_by_griefing	Boolean	false	If true, whether the explosion breaks blocks is affected by the mob griefing game rule

minecraft:hand_container#

This component represents the contents of an entity's hands. The component contains an array of ItemStack JS API Objects representing each slot in the hand container. NOTE: Currently items and containers are read-only. Slot 0 is main-hand Slot 1 is off-hand.

// This example will check the players offhand slot for a specific item after the player attacks an entity.
system.listenForEvent("minecraft:player_attacked_entity", function(eventData) {
    // Get the players hand container
    let handContainer = system.getComponent(eventData.data.player, "minecraft:hand_container");
    // Get the players offhand item
    let offhandItem = handContainer.data[1];
    // Destroy the attacked entity if the player has a totem in their offhand
    if (offhandItem.item == "minecraft:totem") {
        system.destroyEntity(eventData.data.attacked_entity);
    }
});

minecraft:healable#

Defines how the entity can be healed by the player. This doesn't control how much health the entity can have; you must use the Health component for that instead.

Parameters

Name	Type	Default Value	Description
items	Array		The array of items that can be used to heal this entity Name Type Default Value Description item String Item identifier that can be used to heal this entity heal_amount Integer 1 The amount of health this entity gains when fed this item filters Minecraft Filter The filter group that defines the conditions for using this item to heal the entity
force_use	Boolean	false	Determines if item can be used regardless of entity being at full health
filters	Minecraft Filter		The filter group that defines the conditions for this trigger

minecraft:health#

Defines the current and maximum possible health of the entity. Upon applying the component back to the entity the health will change. If it reaches 0 or below the entity will die.

Parameters

Name	Type	Default Value	Description
value	Integer	1	Current health of the entity
max	Integer	10	The maximum health the entity can heal

minecraft:hotbar_container#

This component represents the hotbar contents of a player. The component contains an array of ItemStack JS API Objects representing each slot in the hotbar. NOTE: Currently items and containers are read-only. Slots are ordered left to right.

// This example will check the players first hotbar item slot for a specific item after the player attacks an entity.
system.listenForEvent("minecraft:player_attacked_entity", function(eventData) {
    // Get the players hotbar
    let playerHotbar = system.getComponent(eventData.data.player, "minecraft:hotbar_container");
    // Get the item at the first slot in the hotbar
    let firstHotbarSlot = playerHotbar.data[0];
    // Destroy the attacked entity if the player has an apple in their first hotbar slot
    if (firstHotbarSlot.item == "minecraft:apple") {
        system.destroyEntity(eventData.data.attacked_entity);
    }
});

minecraft:interact#

Defines the ways the player can interact with the entity to which this component is applied.

Parameters

Name	Type	Default Value	Description
spawn_entities	Array		An array of entity identifiers to spawn when the interaction occurs
on_interact	String		An event identifier to fire when the interaction occurs
particle_on_start	JSON Object		Particle effect that will be triggered at the start of the interaction Name Type Default Value Description particle_type String The type of particle that will be spawned particle_y_offset Decimal 0.0 Will offset the particle this amount in the y direction particle_offset_towards_interactor Boolean false Whether or not the particle will appear closer to who performed the interaction
cooldown	Decimal	0.0	Time in seconds before this entity can be interacted with again
swing	Boolean	false	If true, the player will do the 'swing' animation when interacting with this entity
use_item	Boolean	false	If true, the interaction will use an item
hurt_item	Integer	0	The amount of damage the item will take when used to interact with this entity. A value of 0 means the item won't lose durability
interact_text	String		Text to show when the player is able to interact in this way with this entity when playing with Touch-screen controls
add_items	JSON Object		Loot table with items to add to the player's inventory upon successful interaction Name Type Default Value Description table String File path, relative to the behavior pack's path, to the loot table file
spawn_items	JSON Object		Loot table with items to drop on the ground upon successful interaction Name Type Default Value Description table String File path, relative to the behavior pack's path, to the loot table file
transform_to_item	String		The item used will transform to this item upon successful interaction. Format: itemName:auxValue
play_sounds	Array		An array of sound identifiers to play when the interaction occurs

minecraft:inventory#

Defines the entity's inventory (size, restrictions, etc.). Currently this does not allow changing the entity's inventory contents.

Parameters

Name	Type	Default Value	Description
container_type	String	none	Type of container this entity has. Can be horse, minecart_chest, minecart_hopper, inventory, container or hopper
inventory_size	Integer	5	Number of slots the container has
can_be_siphoned_from	Boolean	false	If true, the contents of this inventory can be removed by a hopper
private	Boolean	false	If true, only the entity can access the inventory
restrict_to_owner	Boolean	false	If true, the entity's inventory can only be accessed by its owner or itself
additional_slots_per_strength	Integer	0	Number of slots that this entity can gain per extra strength

minecraft:inventory_container#

This component represents the inventory contents of an entity. The component contains an array of ItemStack JS API Objects representing each slot in the inventory. NOTE: Currently items and containers are read-only.Slot 0-8 is the hotbar, 9-16 is the top row of the player's inventory, 17-24 is the middle row, 25-32 is the bottom row

// This example will check the players third inventory item slot for a specific item after the player attacks an entity.
system.listenForEvent("minecraft:player_attacked_entity", function(eventData) {
    // Get the players inventory
    let playerInventory = system.getComponent(eventData.data.player, "minecraft:inventory_container");
    // Get the item at the third slot in the inventory
    let thirdItemSlot = playerInventory.data[2];
    // Destroy the attacked entity if the player has an apple in their third item slot
    if (thirdItemSlot.item == "minecraft:apple") {
        system.destroyEntity(eventData.data.attacked_entity);
    }
});

minecraft:lookat#

Makes the entity look at another entity. Once applied, if an entity of the specified type is nearby and can be targeted the entity will turn towards it.

Parameters

Name	Type	Default Value	Description
set_target	Boolean	true	If true, this entity will set the attack target as the entity that looked at it
search_radius	Decimal	10.0	Maximum distance this entity will look for another entity looking at it
allow_invulnerable	Boolean	false	If true, invulnerable entities (e.g. Players in creative mode) are considered valid targets
look_cooldown	Range [a, b]	[0.0, 0.0]	The range for the random amount of time during which the entity is 'cooling down' and won't get angered or look for a target
filters	Minecraft Filter	player	Defines the entities that can trigger this component
look_event	String		The event identifier to run when the entities specified in filters look at this entity

minecraft:nameable#

Nameable component describes an entity's ability to be named using a nametag and whether the name shows up or not once applied. Additionally, scripting allows setting the name of the entity directly with the property 'name'.

Parameters

Name	Type	Default Value	Description
name_actions	JSON Object		Describes the special names for this entity and the events to call when the entity acquires those names Name Type Default Value Description on_named String Event to be called when this entity acquires the name specified in 'name_filter' name_filter List List of special names that will cause the events defined in 'on_named' to fire
default_trigger	String		Trigger to run when the entity gets named
alwaysShow	Boolean	false	If true, the name will always be shown
allowNameTagRenaming	Boolean	true	If true, this entity can be renamed with name tags
name	String		The current name of the entity, empty if the entity hasn't been named yet, making this non-empty will apply the name to the entity

minecraft:position#

This component allows you to control an entity's current position in the world. Once applied the entity will be teleported to the new position specified.

Parameters

Name	Type	Default Value	Description
x	Decimal	0.0	Position along the X-Axis (east-west) of the entity
y	Decimal	0.0	Position along the Y-Axis (height) of the entity
z	Decimal	0.0	Position along the Z-Axis (north-south) of the entity

minecraft:rotation#

This component allows you to control an entity's current rotation in the world as well as the entity's head rotation. Once applied, the entity will be rotated as specified.

Parameters

Name	Type	Default Value	Description
x	Decimal	0.0	Controls the head rotation looking up and down
y	Decimal	0.0	Controls the body rotation parallel to the floor

minecraft:shooter#

Defines the entity's ranged attacks. This doesn't allow the entity to use a ranged attack: it only defines what kind of projectile it shoots.

Parameters

Name	Type	Default Value	Description
def	String		Entity identifier to use as projectile for the ranged attack. The entity must have the projectile component to be able to be shot as a projectile
auxVal	Integer	-1	ID of the Potion effect to be applied on hit

minecraft:spawn_entity#

Controls the entity's ability to spawn an entity or an item. This is similar to the chicken's ability to lay eggs after a set amount of time.

Parameters

Name	Type	Default Value	Description
should_leash	Boolean	false	If true, this the spawned entity will be leashed to the parent
num_to_spawn	Integer	1	The number of entities of this type to spawn each time that this triggers
min_wait_time	Integer	300	Minimum amount of time to randomly wait in seconds before another entity is spawned
max_wait_time	Integer	600	Maximum amount of time to randomly wait in seconds before another entity is spawned
spawn_sound	String	plop	Identifier of the sound effect to play when the entity is spawned
spawn_item	String	egg	Item identifier of the item to spawn
spawn_entity	String		Identifier of the entity to spawn, leave empty to spawn the item defined above instead
spawn_method	String	born	Method to use to spawn the entity
spawn_event	String	minecraft:entity_born	Event to call when the entity is spawned
filters	Minecraft Filter		If present, the specified entity will only spawn if the filter evaluates to true
single_use	Boolean	false	If true, this component will only ever spawn the specified entity once

minecraft:tag#

The tag component gives access to the array of entity tags that an entity may have. With this component you can add and remove any of the entity tags.

minecraft:teleport#

This controls the entity's ability to teleport itself (similar to the Enderman). If you wish to teleport the entity once use the Position component instead.

Parameters

Name	Type	Default Value	Description
random_teleports	Boolean	true	If true, the entity will teleport randomly
min_random_teleport_time	Decimal	0.0	Minimum amount of time in seconds between random teleports
max_random_teleport_time	Decimal	20.0	Maximum amount of time in seconds between random teleports
random_teleport_cube	Vector [a, b, c]	[32.0, 16.0, 32.0]	Entity will teleport to a random position within the area defined by this cube
target_distance	Decimal	16.0	Maximum distance the entity will teleport when chasing a target
target_teleport_chance	Decimal	1.0	The chance that the entity will teleport between 0.0 and 1.0. 1.0 means 100%
light_teleport_chance	Decimal	0.01	Modifies the chance that the entity will teleport if the entity is in daylight
dark_teleport_chance	Decimal	0.01	Modifies the chance that the entity will teleport if the entity is in darkness

minecraft:ticking_area_description#

Describes the ticking area's region.

Parameters

Name	Type	Default Value	Description
name	String		The name of the area.
origin	Vector [a, b, c]		The origin position of the area.
is_circle	Boolean		Is the area a circle. If false the area is a square.
radius	Vector [a, b, c]		(if area is a circle) The radius of the area.
max	Vector [a, b, c]		(if area is a square) The edge of the area.

minecraft:tick_world#

The tick world component is a read-only component that allows users to access the ticking areas on entities as well as the ticking area's data.

Parameters

Name	Type	Description
radius	Integer	The radius in chunks of the ticking area
distance_to_players	Decimal	distance_to_players
never_despawn	Boolean	Whether or not this ticking area will despawn when a player is out of range
ticking_area	Entity Ticking Area JS API Object	The ticking area entity that is attached to this entity

Client Components#

These components only run on the client where the script ran and can only be used from client scripts.

minecraft:molang#

The MoLang component gives access to the MoLang variables in an entity. To learn more about MoLang varibles review the add-on documentation. In scripts, you can get and set these varibles that are defined in the entity's JSON files. Because of how the MoLang variables are formatted (variable.isgrazing for example) you must use the [] operator on the object to access the variable. The example below shows how to use the [] operator to access the variable.

Code Example:

let molangComponent = this.createComponent(entity, "minecraft:molang"); 
molangComponent["variable.molangexample"] = 1.0; 
this.applyComponentChanges(molangComponent); 

Block Components#

These components are only found on block objects and can only be on block objects

minecraft:blockstate#

This component contains all the blockstates on a block object. Blockstates control all different aspects of blocks from their orientation to the type of wood they are. Blockstates are represented by numbers, bools, or strings. Please see the Blockstates Documentation to see the valid values for each state. This component allows for the getting and setting of these states.

Code Example:

let blockstateComponent = this.getComponent(block, "minecraft:blockstate");
blockstateComponent.data.coral_color = "blue";
this.applyComponentChanges(block, blockstateComponent);

User-Defined Components#

User-Defined components are a special kind of component that can be defined in script and no built-in game system acts on it.
The component needs to be registered with the Script Engine by giving it a name and a set of fields in the format name:value. Once applied, the component behaves like any of the built-in components: you can get it from an entity, modify its values, and apply the changes.
Currently User-Defined components are the only components that can be dynamically added and removed from an entity using scripts. They don't need to be previously defined in an entity's JSON file. In the current version these components will NOT be saved out or loaded back in: they only exist while the entity is there and need to be added back when reloading the level.

Code Example:

Component Registration

this.registerComponent("myNamespace:myComponent", { myString: "TamerJeison", myInt: 42, myFloat: 1.0, myArray: [1, 2, 3] });

Script Events#

Here you can find the list of events that you can listen for and respond to in your scripts.

Client Events#

Listening Events#

The following Minecraft events are events the Script Engine is listening for and to which you can react in scripts.

minecraft:client_entered_world#

This event is fired whenever a player joins the world. The event data contains the player entity object.

minecraft:hit_result_changed#

This event is triggered whenever the reticle changes from pointing at a block or air to pointing at an entity and the other way around. Up to 1000 blocks away.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that was hit or null if it fired when moving off of an entity
position	Vector [a, b, c]	The position of the entity that was hit or null if it fired when moving off an entity

Code Example:

Responding to hit_result_changed

const mySystem = client.registerSystem(0, 0);

mySystem.initialize = function() {
  this.listenForEvent("minecraft:hit_result_changed", (eventData) => this.onHitChanged(eventData));
};

mySystem.onHitChanged = function(eventData) {
  if(eventData.position != null) {
    let chatEvent = this.createEventData("minecraft:display_chat_event");
    chatEvent.data.message = "Hit at x:" + eventData.position.x + " y:" + eventData.position.y + " z:" + eventData.position.z;
    this.broadcastEvent("minecraft:display_chat_event", chatEvent);
  }
};

minecraft:hit_result_continuous#

This event is triggered every update and tells you what entity the reticle is pointing to in the world up to 1000 blocks away.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that was hit or null if it not pointing at an entity
position	Vector [a, b, c]	The position of the entity that was hit or block that was hit

Code Example:

Responding to hit_result_continuous

const mySystem = client.registerSystem(0, 0);

mySystem.initialize = function() {
  this.listenForEvent("minecraft:hit_result_continuous", (eventData) => this.onHit(eventData));
};

mySystem.onHit = function(eventData) {
  if(eventData.position != null) {
    let chatEvent = this.createEventData("minecraft:display_chat_event");
    chatEvent.data.message = "Position at x:" + eventData.position.x + " y:" + eventData.position.y + " z:" + eventData.position.z;
    this.broadcastEvent("minecraft:display_chat_event", chatEvent);
  }
};

minecraft:pick_hit_result_changed#

This event is triggered whenever the mouse pointer changes from pointing at a block or air to pointing at an entity and the other way around. Up to 1000 blocks away.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that was hit or null if it fired when moving off of an entity
position	Vector [a, b, c]	The position of the entity that was hit or null if it fired when moving off an entity

Code Example:

Responding to pick_hit_result_changed

const mySystem = client.registerSystem(0, 0);

mySystem.initialize = function() {
  this.listenForEvent("minecraft:pick_hit_result_changed", (eventData) => this.onPickChanged(eventData));
};

mySystem.onPickChanged = function(eventData) {
  if(eventData.position != null) {
    let chatEvent = this.createEventData("minecraft:display_chat_event");
    chatEvent.data.message = "Pick at x:" + eventData.position.x + " y:" + eventData.position.y + " z:" + eventData.position.z;
    this.broadcastEvent("minecraft:display_chat_event", chatEvent);
  }
};

minecraft:pick_hit_result_continuous#

This event is triggered every update and tells you what entity the mouse pointer is pointing to in the world up to 1000 blocks away.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that was hit or null if it not pointing at an entity
position	Vector [a, b, c]	The position of the entity that was hit or block that was hit

Code Example:

Responding to pick_hit_result_continuous

const mySystem = client.registerSystem(0, 0);

mySystem.initialize = function() {
  this.listenForEvent("minecraft:pick_hit_result_continuous", (eventData) => this.onPick(eventData));
};

mySystem.onPick = function(eventData) {
  if(eventData.position != null) {
    let chatEvent = this.createEventData("minecraft:display_chat_event");
    chatEvent.data.message = "Pick at:" + eventData.position.x + " y:" + eventData.position.y + " z:" + eventData.position.y + " z:" + eventData.position.z;
    this.broadcastEvent("minecraft:display_chat_event", chatEvent);
  }
};

Trigger-able Events#

The following Minecraft Events can be triggered from scripting and cause the game to respond accordingly.

minecraft:display_chat_event#

This event is used to display a chat message to the specific player that is running the client script. The event data is the message to be displayed in plain text. Special formatting is supported the same way it would be if a player was sending the message.

Parameters

Name	Type	Default Value	Description
message	String		The chat message that will be displayed

Code Example:

Trigger chat event

const mySystem = server.registerSystem(0, 0);

mySystem.update = function() {
  let chatEvent = this.createEventData("minecraft:display_chat_event");
  chatEvent.data.message = "Hello, World!";
  this.broadcastEvent("minecraft:display_chat_event", chatEvent);
};

minecraft:load_ui#

This event is used to show a UI screen to the specific player running the client script. This event will add the UI screen to the top of the UI screen stack. The screen will be shown immediately after the event is triggered. Only screens defined in a HTML file can be shown using this event.

Event Data Parameters

Name	Type	Default Value	Description
path	String		The file path to the screen's HTML file
options	JSON Object		You can define the following options for the screen by setting their value to true or false: always_accepts_input# If true, the screen will always accept and process input for as long as it is in the stack, even if other custom UI screens appear on top of it render_game_behind# If true, the game will continue to be rendered underneath this screen absorbs_input# If true, input will not be passed down to any other screens underneath is_showing_menu# If true, the screen will be treated as the pause menu and the pause menu won't be allowed to show on top of this screen should_steal_mouse# If true, the screen will capture the mouse pointer and limit its movement to the UI screen force_render_below# If true, this screen will be rendered even if another screen is on top of it and will render over them, including the HUD render_only_when_topmost# If true, this screen will only be rendered if it is the screen at the top of the stack

minecraft:send_ui_event#

This event is used to send UI events to the UI Engine for the specific player running the script. After the event is triggered, the UI event will be sent immediately.
Custom UI is based on HTML 5. Review the scripting demo for an example of a custom UI file.

Parameters

Name	Type	Description
eventIdentifier	String	The identifier of the UI event
data	String	The data for the UI event being triggered

minecraft:spawn_particle_attached_entity#

This event is used to create a particle effect that will follow an entity around. This particle effect is only visible to the specific player that is running the client script where you fired the event. Any effect defined in a JSON file (both in your resource pack and in Minecraft) can be used here. MoLang variables defined in the JSON of the effect can then be used to control that effect by changing them in the entity to which it is attached.

Parameters

Name	Type	Default Value	Description
effect	String		The identifier of the particle effect you want to attach to the entity. This is the same name you gave the effect in its JSON file
offset	Vector [a, b, c]	[0, 0, 0]	The offset from the entity's "center" where you want to spawn the effect
entity	Entity JS API Object		The entity object you want to attach the effect to

minecraft:spawn_particle_in_world#

This event is used to create a static particle effect in the world. This particle effect is only visible to the specific player that is running the client script where you fired the event. Any effect defined in a JSON file (both in your resource pack and in Minecraft) can be used here. Once the effect is spawned you won't be able to control it further. Unlike the server version of the event, the client version will spawn the particle in the dimension the player is currently in.

Parameters

Name	Type	Default Value	Description
effect	String		The identifier of the particle effect you want to attach to spawn. This is the same name you gave the effect in its JSON file
position	Vector [a, b, c]	[0, 0, 0]	The position in the world where you want to spawn the effect

minecraft:unload_ui#

This event is used to remove a UI screen from the stack of the specific player running the client script. The event data contains the name of the screen to remove as a string. After the event is triggered the screen will be scheduled to be removed from the stack the next time the UI Engine can do so. Only screens defined in a HTML file can be removed using this event.

minecraft:script_logger_config#

This event is used to turn various levels of logging on and off for client scripts. Note that turning logging on/off is not limited to the script that broadcasted the event. It will affect ALL client scripts including those in other Behavior Packs that are applied to the world. See the Debugging section for more information on logging.

Parameters

Name	Type	Default Value	Description
log_errors	Boolean	false	Set to true to log any scripting errors that occur on the client
log_warnings	Boolean	false	Set to true to log any scripting warnings that occur on the client
log_information	Boolean	false	Set to true to log any general scripting information that occurs on the client. This includes any logging done with client.log()

Server Events#

Listening Events#

The following Minecraft events are events the Script Engine is listening for and to which you can react in scripts.

minecraft:entity_attack#

This event is triggered whenever an entity is being attacked by another entity. This does not guarantee the entity was or will be hurt by the attack.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that attacked
target	Entity JS API Object	The entity that was targeted in the attack

minecraft:player_attacked_entity#

This event is triggered whenever a player attacks an entity.

Parameters

Name	Type	Description
player	Entity JS API Object	The player that attacked an entity
attacked_entity	Entity JS API Object	The entity that was attacked by the player

minecraft:entity_acquired_item#

This event is triggered whenever an entity acquires an item.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity who acquired the item
item_stack	ItemStack JS API Object	The item that was acquired
acquisition_method	String	The way the entity acquired the item
acquired_amount	Integer	The total number of items acquired by the entity during this event
secondary_entity	Entity JS API Object	If it exists, the entity that affected the item before it was acquired. Example: A player completes a trade with a villager. The `entity` property would be the player and the `secondary_entity` would be the villager

minecraft:entity_carried_item_changed#

This event is triggered whenever an entity changes the item carried in their hand.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that changed what they were carrying
previous_carried_item	ItemStack JS API Object	The item that was previously in the entities hands
carried_item	ItemStack JS API Object	The item that is now in the entities hands

minecraft:entity_created#

This event is triggered whenever an entity is added to the world.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that was just created

minecraft:entity_death#

This event is triggered whenever an entity dies. This won't be triggered when an entity is removed (such as when using destroyEntity). Not all of these values are present with every entity death.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that died
killer	Entity JS API Object	The entity that killed the entity
block_position	JavaScript Object	The position of the block that killed the entity
cause	String	The cause of the entity's death
projectile_type	String	The type of the projectile that killed the entity

minecraft:entity_dropped_item#

This event is triggered whenever an entity drops an item.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity who dropped the item
item_stack	ItemStack JS API Object	The item that was dropped

minecraft:entity_equipped_armor#

This event is triggered whenever an entity equips an item in their armor slots.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity who is equipping the armor
item_stack	ItemStack JS API Object	The armor that is being equipped

minecraft:entity_hurt#

This event is triggered whenever an entity is hurt.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that took damage
cause	String	The way the entity took damage. Refer to the Damage Source documentation for a complete list of sources
attacker	Entity JS API Object	Present only when damaged by an entity or projectile. The entity that attacked and caused the damage
projectile_type	String	Present only when damaged by a projectile. This is the identifier of the projectile that hit the entity
block_position	Vector [a, b, c]	Present only when damaged by a block. This is the position of the block that hit the entity
damage	Integer	The amount of damage the entity took after immunity and armor are taken into account
absorbed_damage	Integer	The amount the damage was reduced by by the entity's absorption effect

minecraft:entity_sneak#

This event is triggered whenever an entity flag's value changes.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that changed their sneaking state
sneaking	Boolean	If true, the entity just started sneaking. If false, the entity just stopped sneaking

minecraft:entity_start_riding#

This event is triggered whenever an entity becomes a rider on another entity.

Parameters

Name	Type	Description
entity	Entity JS API Object	The rider
ride	Entity JS API Object	The entity being ridden

minecraft:entity_stop_riding#

This event is triggered whenever an entity stops riding another entity.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that was riding another entity
exit_from_rider	Boolean	If true, the rider stopped riding by their own decision
entity_is_being_destroyed	Boolean	If true, the rider stopped riding because they are now dead
switching_rides	Boolean	If true, the rider stopped riding because they are now riding a different entity

minecraft:entity_tick#

This event is triggered whenever an entity is ticked. This event will not fire when a player is ticked.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that was ticked

minecraft:entity_use_item#

This event is triggered whenever an entity uses an item.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity who is using the item
item_stack	ItemStack JS API Object	The item that is being used
use_method	String	The way the entity used the item

minecraft:block_destruction_started#

This event is triggered whenever a player starts to destroy a block.

Parameters

Name	Type	Description
player	Entity JS API Object	The player that started destoying the block
block_position	JavaScript Object	The position of the block that is being destroyed

minecraft:block_destruction_stopped#

This event is triggered whenever a player stops destroying a block.

Parameters

Name	Type	Description
player	Entity JS API Object	The player that stopped destoying the block
block_position	JavaScript Object	The position of the block that was being destroyed
destruction_progress	Decimal	How far along the destruction was before it was stopped (0 - 1 range)

minecraft:block_exploded#

This event is triggered whenever a block is destroyed by an explosion.

Parameters

Name	Type	Description
entity	Entity JS API Object	The entity that exploded
block_position	JavaScript Object	The position of the block that was destroyed by the explosion
block_identifier	String	The identifier of the block that was destroyed
cause	String	The cause of the block's destruction

minecraft:block_interacted_with#

This event is triggered whenever a player interacts with a block.

Parameters

Name	Type	Description
player	Entity JS API Object	The player that interacted with the block
block_position	JavaScript Object	The position of the block that is being interacted with

minecraft:piston_moved_block#

This event is triggered whenever a piston moves a block.

Parameters

Name	Type	Description
piston_position	JavaScript Object	The position of the piston that moved the block
block_position	JavaScript Object	The position of the block that was moved
piston_action	String	The action the piston took, "extended" or "retracted"

minecraft:player_destroyed_block#

This event is triggered whenever a player destroys a block.

Parameters

Name	Type	Description
player	Entity JS API Object	The player that destroyed the block
block_position	JavaScript Object	The position of the block that was destroyed
block_identifier	String	The identifier of the block that was destroyed

minecraft:player_placed_block#

This event is triggered whenever a player places a block.

Parameters

Name	Type	Description
player	Entity JS API Object	The player that placed the block
block_position	JavaScript Object	The position of the block that was placed

minecraft:play_sound#

This event is used to play a sound effect. Currently, sounds can only be played at a fixed position in the world. Global sounds and sounds played by an entity will be supported in a later update.

Parameters

Name	Type	Default Value	Description
sound	String		The identifier of the sound you want to play. Only sounds defined in the applied resource packs can be played
volume	Decimal	1.0	The volume of the sound effect. A value of 1.0 will play the sound effect at the volume it was recorded at
pitch	Decimal	1.0	The pitch of the sound effect. A value of 1.0 will play the sound effect with regular pitch
position	Vector [a, b, c]	[0, 0, 0]	The position in the world we want to play the sound at

minecraft:projectile_hit#

This event is triggered whenever a projectile hits something.

Parameters

Name	Type	Description
projectile	Entity JS API Object	The projectile in question
owner	Entity JS API Object	The entity that fired the projectile
entity	Entity JS API Object	The entity that was hit by the projectile, if any
position	Vector [a, b, c]	The position of the collision

minecraft:weather_changed#

This event is triggered whenever the weather changes. It contains information about the weather it is changing to.

Parameters

Name	Type	Description
dimension	String	The name of the dimension where the weather change happened
raining	Boolean	Tells if the new weather has rain
lightning	Boolean	Tells if the new weather has lightning

Trigger-able Events#

The following Minecraft events can be triggered from scripting and the game will respond, accordingly.

minecraft:entity_definition_event#

This event is used to trigger events that Entity Definition JSON files are listening for. For example, you can trigger the minecraft:become_charged event on a creeper to turn it into a charged creeper.

Parameters

Name	Type	Default Value	Description
entity	Entity JS API Object		The entity object you want to attach the effect to
event	String		The identifier of the event to trigger on that entity. Both built-in (minecraft:) and custom events are supported

minecraft:display_chat_event#

This event is used to send a chat message from the server to the players. The event data is the message being sent as a string. Special formatting is supported the same way it would be if a player was sending the message.

Parameters

Name	Type	Default Value	Description
message	String		The chat message that will be displayed

minecraft:execute_command#

This event is used to execute a slash command on the server with the World Owner permission level. The event data contains the slash command as a string. The slash command will be processed and will run after the event is sent.

Parameters

Name	Type	Default Value	Description
command	String		The command that will be run

minecraft:play_sound#

This event is used to play a sound effect. Currently, sounds can only be played at a fixed position in the world. Global sounds and sounds played by an entity will be supported in a later update.

Parameters

Name	Type	Default Value	Description
sound	String		The identifier of the sound you want to play. Only sounds defined in the applied resource packs can be played
volume	Decimal	1.0	The volume of the sound effect. A value of 1.0 will play the sound effect at the volume it was recorded at
pitch	Decimal	1.0	The pitch of the sound effect. A value of 1.0 will play the sound effect with regular pitch
position	Vector [a, b, c]	[0, 0, 0]	The position in the world we want to play the sound at

minecraft:spawn_particle_attached_entity#

This event is used to create a particle effect that will follow an entity around. This particle effect is visible to all players. Any effect defined in a JSON file (both in your resource pack and in Minecraft) can be used here. MoLang variables defined in the JSON of the effect can then be used to control that effect by changing them in the entity to which it is attached.

Parameters

Name	Type	Default Value	Description
effect	String		The identifier of the particle effect you want to attach to the entity. This is the same identifier you gave the effect in its JSON file
offset	Vector [a, b, c]	[0, 0, 0]	The offset from the entity's "center" where you want to spawn the effect
entity	Entity JS API Object		The entity object you want to attach the effect to

minecraft:spawn_particle_in_world#

This event is used to create a static particle effect in the world. This particle effect is visible to all players. Any effect defined in a JSON file (both in your resource pack and in Minecraft) can be used here. Once the effect is spawned you won't be able to control it further.

Parameters

Name	Type	Default Value	Description
effect	String		The identifier of the particle effect you want to attach to spawn. This is the same name you gave the effect in its JSON file
position	Vector [a, b, c]	[0, 0, 0]	The position in the world where you want to spawn the effect
dimension	String	overworld	The dimension in which you want to spawn the effect. Can be "overworld", "nether", or "the end"

minecraft:script_logger_config#

This event is used to turn various levels of logging on and off for server scripts. Note that turning logging on/off is not limited to the script that broadcasted the event. It will affect ALL server scripts including those in other Behavior Packs that are applied to the world. See the Debugging section for more information on logging.

Parameters

Name	Type	Default Value	Description
log_errors	Boolean	false	Set to true to log any scripting errors that occur on the server
log_warnings	Boolean	false	Set to true to log any scripting warnings that occur on the server
log_information	Boolean	false	Set to true to log any general scripting information that occurs on the server. This includes any logging done with server.log()