# removeMessageHandler()

Unmounts the message-handling function.

When using React, it’s necessary to unmount functions to remove them from the DOM and perform necessary cleanup.

## Sample

Used within a JavaScript app uploaded as a static resource and referenced by `lightning:container`, this example unmounts a message handling function.

```javascript
componentWillUnmount() {
  LCC.removeMessageHandler(this.onMessage);
}
```

## Arguments

| Name                              | Type     | Description                                                      |
| --------------------------------- | -------- | ---------------------------------------------------------------- |
| `handler: (userMsg: any) => void` | function | The function that handles messages sent from the Aura component. |

## Response

None.