@loopback/docs/site/apidocs/express.invokemiddlewareoptions.validate.md

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title: 'API docs: express.invokemiddlewareoptions.validate'
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[Home](./index.md) &gt; [@loopback/express](./express.md) &gt; [InvokeMiddlewareOptions](./express.invokemiddlewareoptions.md) &gt; [validate](./express.invokemiddlewareoptions.validate.md)

## InvokeMiddlewareOptions.validate property

An optional function to validate the sorted groups before invoking the middleware chain

<b>Signature:</b>

```typescript
validate?: (groups: string[]) => void;
```