---
title: "PropertyCallback | 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 PropertyCallback

PropertyCallback: (  
    a: {  
        key: string;  
        path: \[string, "paint" | "layout", string\];  
        reference: [StylePropertySpecification](https://docs.maptiler.com/sdk-js/api-reference/types/StylePropertySpecification/) | null;  
        set: (  
            a:  
                | [PropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/PropertyValueSpecification/)<unknown\>  
                | [DataDrivenPropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/DataDrivenPropertyValueSpecification/)<unknown\>,  
        ) \=> void;  
        value:  
            | [PropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/PropertyValueSpecification/)<unknown\>  
            | [DataDrivenPropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/DataDrivenPropertyValueSpecification/)<unknown\>;  
    },  
) \=> void

#### Type Declaration

-   -   (  
            a: {  
                key: string;  
                path: \[string, "paint" | "layout", string\];  
                reference: [StylePropertySpecification](https://docs.maptiler.com/sdk-js/api-reference/types/StylePropertySpecification/) | null;  
                set: (  
                    a:  
                        | [PropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/PropertyValueSpecification/)<unknown\>  
                        | [DataDrivenPropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/DataDrivenPropertyValueSpecification/)<unknown\>,  
                ) \=> void;  
                value:  
                    | [PropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/PropertyValueSpecification/)<unknown\>  
                    | [DataDrivenPropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/DataDrivenPropertyValueSpecification/)<unknown\>;  
            },  
        ): void
    -   #### Parameters
        
        -   a: {  
                key: string;  
                path: \[string, "paint" | "layout", string\];  
                reference: [StylePropertySpecification](https://docs.maptiler.com/sdk-js/api-reference/types/StylePropertySpecification/) | null;  
                set: (  
                    a:  
                        | [PropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/PropertyValueSpecification/)<unknown\>  
                        | [DataDrivenPropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/DataDrivenPropertyValueSpecification/)<unknown\>,  
                ) \=> void;  
                value:  
                    | [PropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/PropertyValueSpecification/)<unknown\>  
                    | [DataDrivenPropertyValueSpecification](https://docs.maptiler.com/sdk-js/api-reference/types/DataDrivenPropertyValueSpecification/)<unknown\>;  
            }
        
        #### Returns void