---
title: "MessageHandler | 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.

# Type Alias MessageHandler<T>

MessageHandler: (  
    mapId: string | number,  
    params: [RequestResponseMessageMap](https://docs.maptiler.com/sdk-js/api-reference/types/RequestResponseMessageMap/)\[[T](#t)\]\[0\],  
    abortController?: AbortController,  
) \=> Promise<[RequestResponseMessageMap](https://docs.maptiler.com/sdk-js/api-reference/types/RequestResponseMessageMap/)\[[T](#t)\]\[1\]\>

#### Type Parameters

-   T extends [MessageType](https://docs.maptiler.com/sdk-js/api-reference/enums/MessageType/)

#### Type Declaration

-   -   (  
            mapId: string | number,  
            params: [RequestResponseMessageMap](https://docs.maptiler.com/sdk-js/api-reference/types/RequestResponseMessageMap/)\[[T](#t)\]\[0\],  
            abortController?: AbortController,  
        ): Promise<[RequestResponseMessageMap](https://docs.maptiler.com/sdk-js/api-reference/types/RequestResponseMessageMap/)\[[T](#t)\]\[1\]\>
    -   #### Parameters
        
        -   mapId: string | number
        -   params: [RequestResponseMessageMap](https://docs.maptiler.com/sdk-js/api-reference/types/RequestResponseMessageMap/)\[[T](#t)\]\[0\]
        -   `Optional`abortController: AbortController
        
        #### Returns Promise<[RequestResponseMessageMap](https://docs.maptiler.com/sdk-js/api-reference/types/RequestResponseMessageMap/)\[[T](#t)\]\[1\]\>