# On

User events are overridden by name and weight, sorted by weight (desc) and must be namespaced.

```javascript
class Foo {

  @on('axon__task.completed',  {   
    environment: 'development',   
  })
  static check(...params, runtime) {
    const {
      weight, 
      source,   // "script" or "event" 
      metadata,
      event,   
      context   // the event document, when fired by a user event.
    } = runtime

    console.log('checking')
  }

}
```

### script.fire(event, ...params)

Execute events registered with `@on` in the ***same script context*** as the current principal.

*Arguments*

* `event` { String\[] } The custom event name. eg. `axon__task.completed.before`
* `...params` { \*\[] } Options object to pass to `script.arguments`

### @on(event, options)

*Arguments*

* `event` { String } Event
* `options` { Object } Options object
  * `active` { Boolean = *true* }
  * `name` { String }
  * `label` { String }  
  * `environment` { String = *"\*"* }
  * `if` { Expression }
  * `weight` { Number = *0* }    

## Examples

```javascript
const { on } = require('decorators')

class Handler {

  @on('axon__task.completed', { name: 'axon__task_completed_event' })
  onCompleted( task, str ) {
    // str === "another param"
  }

}

const task = completeATask()
script.fire('axon__task.completed', task, "another param")
```