# Constructor

## Appmixer

| Method                                      | Description                                                                                                                                                                                                                                                     |
| ------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `Appmixer({ baseUrl })`                     | A constructor function to create an instance of the Appmixer SDK. Pass the base URL of the engine (Appmixer API).                                                                                                                                               |
| `appmixer.set(key, value)`                  | Set a property on the appmixer SDK object. Currently only `accessToken` should be set to be able to make calls to the Appmixer API.                                                                                                                             |
| `appmixer.onInvalidAccessToken(callbackFn)` | Allows setting a callback function that will be called whenever the current access token on the SDK is not valid. More information can be found on the [Managing Authentication ](/6.0/v4/tutorials/managing-authentication.md#check-token-expiration)tutorial. |


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