---
id: fast-foundation.elementdefinitionparams.baseclass
title: ElementDefinitionParams.baseClass property
hide_title: true
---
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[@microsoft/fast-foundation](./fast-foundation.md) &gt; [ElementDefinitionParams](./fast-foundation.elementdefinitionparams.md) &gt; [baseClass](./fast-foundation.elementdefinitionparams.baseclass.md)

## ElementDefinitionParams.baseClass property

FAST actual base class instance.

<b>Signature:</b>

```typescript
readonly baseClass?: Constructable;
```