---
id: fast-foundation.elementdefinitioncallback
title: ElementDefinitionCallback type
hide_title: true
---
<!-- Do not edit this file. It is automatically generated by API Documenter. -->

[@microsoft/fast-foundation](./fast-foundation.md) &gt; [ElementDefinitionCallback](./fast-foundation.elementdefinitioncallback.md)

## ElementDefinitionCallback type

The callback type that is invoked when an element can be defined by a design system.

<b>Signature:</b>

```typescript
export declare type ElementDefinitionCallback = (ctx: ElementDefinitionContext) => void;
```