> For the complete documentation index, see [llms.txt](https://docs.appmixer.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.appmixer.com/6.0/6.3/appmixer-ui-sdk/custom-api.md).

# Custom API

Appmixer SDK allows you to override API methods used by the SDK instance. This can be handy in edge case scenarios where you need to override the API requests and their parameters or response values.

## Setting a custom API option

Custom API is represented as an object composed of **asynchronous** methods that you set on your Appmixer SDK instance using the `api` option:

```javascript
var myCustomApi = {
  /* the key must match an existing API method */
  myCustomApiMethod(/* arguments of the original method */) {
    return new Promise((resolve) => {
      resolve(myCustomResponse);
    });
  }
}

/* Use a custom API on the entire SDK instance */
var appmixer = new Appmixer({ api: myCustomApi });

/* Use a custom API on a particular SDK UI widget */
var designer = new appmixer.ui.Designer({ api: myCustomApi });
```

The list of API methods can be found [here](/6.0/6.3/appmixer-ui-sdk/api-module.md#methods).

An example how to redefine the flow update request.

```javascript
/* Create "Designer". */
var designer = appmixer.ui.Designer({
    el: '#your-designer',
    options: designerOptions(),
    api: {
        // extending the updateFlow request
        updateFlow(flowId, update) {
            // at this place you can call your own API every time the flow 
            // gets updated
            // carefully catch errors, timeouts ... so calling your 
            // external API does not affect the Designer behaviour
            console.log('Calling your own API.');
            console.log(JSON.parse(JSON.stringify(update)));

            // in order to update the flow in Appmixer, call the Flow API
            return this._request({
                url: `${this.get('baseUrl')}/flows/${flowId}`,
                method: 'PUT',
                data: update
            });
        }
    }
});
```


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