Function eventField

eventField<TFieldValue>(targetOrQuery, eventName, fieldName, initialValue, options?): Reactive<TFieldValue>
Fired when eventName fires on target.

Rather than whole event args being emitted on the stream, it plucks a field from the event args, or if that's missing, from the target.
```
// Emits the the value of a field named 'x'
// on the change event args
eventField(el, `pointermove`, `x`);
```
Type Parameters
- TFieldValue = string
Parameters
- targetOrQuery: null | string | EventTarget
  Event target, HTML element or HTML query (eg '#someId')
- eventName: string
  Name of event, eg. 'pointermove'
- fieldName: string
  Name of field, eg 'x'
- initialValue: TFieldValue
  Initial data
- options: Partial<EventOptions & InitStreamOptions & {
  fallbackFieldValue: TFieldValue;
  fallbackObject: any;
  }> = {}
  Options for source
Returns Reactive<TFieldValue>