gr-event-dispatcher

eventDispatcher

JavaScript events for custom objects

Install

npm

$ npm install gr-event-dispatcher

API

• eventDispatcher
  • ~addEventListener(type, listener) ⇒ Object
  • ~hasEventListener(type, listener) ⇒ Boolean
  • ~removeEventListener(type, listener) ⇒ Object
  • ~dispatchEvent(event) ⇒ Object
  • ~apply(object) ⇒ Object

eventDispatcher~addEventListener(type, listener) ⇒ Object

Registers the specified listener on the event target it's called on.

Kind: inner method of eventDispatcher
Returns: Object - The eventDispatcher object.
Throws:

• TypeError If the object that eventDispatcher is applied to is not extensible.

Param	Type	Description
type	String	A string representing the event type to listen for.
listener	function	A function to be executed when an event of the specified type occurs.

eventDispatcher~hasEventListener(type, listener) ⇒ Boolean

Checks if the target object has a listener registered on for specific event type.

Kind: inner method of eventDispatcher
Returns: Boolean - True if target object has listener registered for specific event type; otherwise false.

Param	Type	Description
type	String	A string representing the event type.
listener	function	The event listener to check if registered for the specified event type.

eventDispatcher~removeEventListener(type, listener) ⇒ Object

Removes the previously registered event listener from the event target.

Kind: inner method of eventDispatcher
Returns: Object - The eventDispatcher object.

Param	Type	Description
type	String	A string representing the event type to remove.
listener	function	The event listener function to remove from the event target.

eventDispatcher~dispatchEvent(event) ⇒ Object

Dispatches an event at the specified event target.

Kind: inner method of eventDispatcher
Returns: Object - The eventDispatcher object.

Param	Type	Description
event	Object	The event object to be dispatched.

eventDispatcher~apply(object) ⇒ Object

Applies the eventDispatcher prototype methods to the event target.

Kind: inner method of eventDispatcher
Returns: Object - The eventDispatcher object.
Throws:

• TypeError If the object that eventDispatcher is applied to is not extensible.

Param	Type	Description
object	Object	The event target object.

Example

var car = {
  start: function (afterStartCallback) {
    // Dispatch `start` event.
    this.dispatchEvent({type: 'start', message: 'Start engines'});
    afterStartCallback && afterStartCallback(this);
  },
  stop: function () {
    // Dispatch `stop` event.
    this.dispatchEvent({type: 'stop', message: 'Stop engines'});
  }
};

function startEngines(event) {
  console.log(event.message);
}

function stopEngines(event) {
  console.log(event.message);
}

// Apply `eventDispatcher` methods to the prototype of the event target.
eventDispatcher.apply(Object.getPrototypeOf(car));

// Register event listeners to event target.
car
  .addEventListener('start', startEngines)
  .addEventListener('afterStart', startEngines)
  .addEventListener('stop', stopEngines);

// `start` event fires first, then `afterStart` and finally
// after two seconds `stop` events fires.

car.start(function (self) {
  // Dispatch `afterStart` event.
  self.dispatchEvent({type: 'afterStart', message: 'Car has started'});
});

console.log(car.hasEventListener('start', startEngines));      // -> true
console.log(car.hasEventListener('afterStart', startEngines)); // -> true
console.log(car.hasEventListener('stop', startEngines));       // -> false
console.log(car.hasEventListener('stop', stopEngines));        // -> true

setTimeout(function () {
  car.stop();

  // Remove all event listeners from event target.
  car
    .removeEventListener('start', startEngines)
    .removeEventListener('afterStart', startEngines)
    .removeEventListener('stop', stopEngines);
}, 2000);