---
title: "Worker | JavaScript maps SDK"
description: "Documentation for MapTiler SDK"
---

> For AI agents: a documentation index is available at [/llms.txt](https://docs.maptiler.com/llms.txt). Markdown versions of all pages are available by appending .md to any URL.

# Interface Worker

The **`Worker`** interface of the Web Workers API represents a background task that can be created via script, which can send messages back to its creator.

[MDN Reference](https://developer.mozilla.org/docs/Web/API/Worker)

interface Worker {  
    [onerror](#onerror): ((this: [AbstractWorker](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/), ev: ErrorEvent) \=> any) | null;  
    [onmessage](#onmessage): ((this: Worker, ev: MessageEvent) \=> any) | null;  
    [onmessageerror](#onmessageerror): ((this: Worker, ev: MessageEvent) \=> any) | null;  
    [addEventListener](#addeventlistener-1)<[K](#addeventlistenerk) extends keyof [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)\>(  
        type: [K](#addeventlistenerk),  
        listener: (this: Worker, ev: [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)\[[K](#addeventlistenerk)\]) \=> any,  
        options?: boolean | AddEventListenerOptions,  
    ): void;  
    [addEventListener](#addeventlistener-2)(  
        type: string,  
        listener: [EventListenerOrEventListenerObject](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.EventListenerOrEventListenerObject/),  
        options?: boolean | AddEventListenerOptions,  
    ): void;  
    [dispatchEvent](#dispatchevent-1)(event: Event): boolean;  
    [postMessage](#postmessage-1)(message: any, transfer: [Transferable](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.Transferable/)\[\]): void;  
    [postMessage](#postmessage-2)(message: any, options?: [StructuredSerializeOptions](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.StructuredSerializeOptions/)): void;  
    [removeEventListener](#removeeventlistener-1)<[K](#removeeventlistenerk) extends keyof [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)\>(  
        type: [K](#removeeventlistenerk),  
        listener: (this: Worker, ev: [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)\[[K](#removeeventlistenerk)\]) \=> any,  
        options?: boolean | EventListenerOptions,  
    ): void;  
    [removeEventListener](#removeeventlistener-2)(  
        type: string,  
        listener: [EventListenerOrEventListenerObject](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.EventListenerOrEventListenerObject/),  
        options?: boolean | EventListenerOptions,  
    ): void;  
    [terminate](#terminate-1)(): void;  
}

#### Hierarchy ([View Summary](https://docs.maptiler.com/sdk-js/api-reference/hierarchy/#Externals.Worker))

-   EventTarget
-   [AbstractWorker](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/)
-   [MessageEventTarget](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.MessageEventTarget/)<Worker\>
    -   Worker

##### Index

### Properties[](#properties)

[onerror](#onerror) [onmessage](#onmessage) [onmessageerror](#onmessageerror)

### Methods[](#methods)

[addEventListener](#addeventlistener) [dispatchEvent](#dispatchevent) [postMessage](#postmessage) [removeEventListener](#removeeventlistener) [terminate](#terminate)

## Properties[](#properties-1)

### onerror[](#onerror)

onerror: ((this: [AbstractWorker](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/), ev: ErrorEvent) \=> any) | null

[MDN Reference](https://developer.mozilla.org/docs/Web/API/ServiceWorker/error_event)

Inherited from [AbstractWorker](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/).[onerror](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/#onerror)

### onmessage[](#onmessage)

onmessage: ((this: Worker, ev: MessageEvent) \=> any) | null

[MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event)

Inherited from [MessageEventTarget](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.MessageEventTarget/).[onmessage](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.MessageEventTarget/#onmessage)

### onmessageerror[](#onmessageerror)

onmessageerror: ((this: Worker, ev: MessageEvent) \=> any) | null

[MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event)

Inherited from [MessageEventTarget](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.MessageEventTarget/).[onmessageerror](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.MessageEventTarget/#onmessageerror)

## Methods[](#methods-1)

### addEventListener[](#addeventlistener)

-   addEventListener<[K](#addeventlistenerk) extends keyof [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)\>(  
        type: [K](#addeventlistenerk),  
        listener: (this: Worker, ev: [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)\[[K](#addeventlistenerk)\]) \=> any,  
        options?: boolean | AddEventListenerOptions,  
    ): void[](#addeventlistener-1)
    
    The **`addEventListener()`** method of the EventTarget interface sets up a function that will be called whenever the specified event is delivered to the target.
    
    [MDN Reference](https://developer.mozilla.org/docs/Web/API/EventTarget/addEventListener)
    
    #### Type Parameters
    
    -   K extends keyof [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)
    
    #### Parameters
    
    -   type: [K](#addeventlistenerk)
    -   listener: (this: Worker, ev: [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)\[[K](#addeventlistenerk)\]) \=> any
    -   `Optional`options: boolean | AddEventListenerOptions
    
    #### Returns void
    
    Overrides [AbstractWorker](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/).[addEventListener](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/#addeventlistener)
    
-   addEventListener(  
        type: string,  
        listener: [EventListenerOrEventListenerObject](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.EventListenerOrEventListenerObject/),  
        options?: boolean | AddEventListenerOptions,  
    ): void[](#addeventlistener-2)
    
    The **`addEventListener()`** method of the EventTarget interface sets up a function that will be called whenever the specified event is delivered to the target.
    
    [MDN Reference](https://developer.mozilla.org/docs/Web/API/EventTarget/addEventListener)
    
    #### Parameters
    
    -   type: string
    -   listener: [EventListenerOrEventListenerObject](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.EventListenerOrEventListenerObject/)
    -   `Optional`options: boolean | AddEventListenerOptions
    
    #### Returns void
    
    Overrides [AbstractWorker](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/).[addEventListener](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/#addeventlistener)
    

### dispatchEvent[](#dispatchevent)

-   dispatchEvent(event: Event): boolean[](#dispatchevent-1)
    
    The **`dispatchEvent()`** method of the EventTarget sends an Event to the object, (synchronously) invoking the affected event listeners in the appropriate order. The normal event processing rules (including the capturing and optional bubbling phase) also apply to events dispatched manually with dispatchEvent().
    
    [MDN Reference](https://developer.mozilla.org/docs/Web/API/EventTarget/dispatchEvent)
    
    #### Parameters
    
    -   event: Event
    
    #### Returns boolean
    
    Inherited from EventTarget.dispatchEvent
    

### postMessage[](#postmessage)

-   postMessage(message: any, transfer: [Transferable](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.Transferable/)\[\]): void[](#postmessage-1)
    
    The **`postMessage()`** method of the Worker interface sends a message to the worker. The first parameter is the data to send to the worker. The data may be any JavaScript object that can be handled by the structured clone algorithm.
    
    [MDN Reference](https://developer.mozilla.org/docs/Web/API/Worker/postMessage)
    
    #### Parameters
    
    -   message: any
    -   transfer: [Transferable](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.Transferable/)\[\]
    
    #### Returns void
    
-   postMessage(message: any, options?: [StructuredSerializeOptions](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.StructuredSerializeOptions/)): void[](#postmessage-2)
    
    #### Parameters
    
    -   message: any
    -   `Optional`options: [StructuredSerializeOptions](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.StructuredSerializeOptions/)
    
    #### Returns void
    

### removeEventListener[](#removeeventlistener)

-   removeEventListener<[K](#removeeventlistenerk) extends keyof [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)\>(  
        type: [K](#removeeventlistenerk),  
        listener: (this: Worker, ev: [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)\[[K](#removeeventlistenerk)\]) \=> any,  
        options?: boolean | EventListenerOptions,  
    ): void[](#removeeventlistener-1)
    
    The **`removeEventListener()`** method of the EventTarget interface removes an event listener previously registered with EventTarget.addEventListener() from the target. The event listener to be removed is identified using a combination of the event type, the event listener function itself, and various optional options that may affect the matching process; see Matching event listeners for removal.
    
    [MDN Reference](https://developer.mozilla.org/docs/Web/API/EventTarget/removeEventListener)
    
    #### Type Parameters
    
    -   K extends keyof [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)
    
    #### Parameters
    
    -   type: [K](#removeeventlistenerk)
    -   listener: (this: Worker, ev: [WorkerEventMap](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.WorkerEventMap/)\[[K](#removeeventlistenerk)\]) \=> any
    -   `Optional`options: boolean | EventListenerOptions
    
    #### Returns void
    
    Overrides [AbstractWorker](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/).[removeEventListener](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/#removeeventlistener)
    
-   removeEventListener(  
        type: string,  
        listener: [EventListenerOrEventListenerObject](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.EventListenerOrEventListenerObject/),  
        options?: boolean | EventListenerOptions,  
    ): void[](#removeeventlistener-2)
    
    The **`removeEventListener()`** method of the EventTarget interface removes an event listener previously registered with EventTarget.addEventListener() from the target. The event listener to be removed is identified using a combination of the event type, the event listener function itself, and various optional options that may affect the matching process; see Matching event listeners for removal.
    
    [MDN Reference](https://developer.mozilla.org/docs/Web/API/EventTarget/removeEventListener)
    
    #### Parameters
    
    -   type: string
    -   listener: [EventListenerOrEventListenerObject](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.EventListenerOrEventListenerObject/)
    -   `Optional`options: boolean | EventListenerOptions
    
    #### Returns void
    
    Overrides [AbstractWorker](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/).[removeEventListener](https://docs.maptiler.com/sdk-js/api-reference/interfaces/Externals.AbstractWorker/#removeeventlistener)
    

### terminate[](#terminate)

-   terminate(): void[](#terminate-1)
    
    The **`terminate()`** method of the Worker interface immediately terminates the Worker. This does not offer the worker an opportunity to finish its operations; it is stopped at once.
    
    [MDN Reference](https://developer.mozilla.org/docs/Web/API/Worker/terminate)
    
    #### Returns void