---
title: "Function trigger | Customer's Canvas On-Premises"
canonical: "https://customerscanvas.com/docs/on-premises/ui-framework/widgets/function-trigger/"
---

# Function trigger

> This non-visual widget is used to execute synchronous or async functions when the input parameters change.

## General info

- **type**: `function-trigger`

## Params

- `arguments` - an array of parameters, change of which should trigger specified callbacks.
- `callback` - a function `("{{#function <expression>}}")` or an array of functions that are executed when the `arguments` change.
- `catch` - a function `("{{#function <expression>}}")` or an array of functions that are executed if the `callback` fails.
- `enabled ` - if `false`, the `callback` will not be executed. The default value is `true`.
- `finally` - a function `("{{#function <expression>}}")` or an array of functions that are executed after the `callback`, regardless of its outcome.
- `lock ` - names of widgets that should be locked while waiting for the `callback`. The editor will display a preloader on this widget.

## Example

Now, let's see how you can handle the result of selecting an option. Once an option is changed, the `function-trigger` widget will output its title to the console.

```json
{
  "widgets": [
    {
      "name": "options",
      "type": "option",
      "params": {
          "type": "list",
          "title": "Name",
          "prompt": "Choose a name",
          "values": [
              { "title": "Jack" },
              { "title": "James" },
              { "title": "John" }
          ]
      }
    },
    {
      "name": "option-titles",
      "type": "function-trigger",
      "enabled": false,
      "lock": [],
      "params": {
        "arguments": [
          "{{ $['options']._.title }}",
          "{{ $['options']._.title }}"
        ],
        "callback": [
          "{{ #function(var1,var2) console.log(var1,var2) }}"
        ],
        "catch": [
          "{{ #function console.error('failed') }}"
        ],
        "finally": [
          "{{ #function console.log('cleanup') }}"
        ]
      }
    }
  ]
}
```

---
You can find more details about the properties of this widget in [AuWidgetFunctionTrigger](https://customerscanvas.com/docs/on-premises/ui-framework/widgets/reference/au-widget-function-trigger.au-widget-function-trigger.md#auwidgetfunctiontrigger).

For more details about configuration parameters, refer to [IAuWidgetFunctionTriggerConfig](https://customerscanvas.com/docs/on-premises/ui-framework/widgets/reference/au-widget-function-trigger.IAuWidgetFunctionTriggerConfig.md#iauwidgetfunctiontriggerconfig).