Event - Cesium Documentation

# Event

#### new Event()

  A generic utility class for managing subscribers for a particular event. This class is usually instantiated inside of a container class and exposed as a property for others to subscribe to.

  ##### Example:

      MyObject.prototype.myListener = function(arg1, arg2) {
          this.myArg1Copy = arg1;
          this.myArg2Copy = arg2;
      }

      var myObjectInstance = new MyObject();
      var evt = new Cesium.Event();
      evt.addEventListener(MyObject.prototype.myListener, myObjectInstance);
      evt.raiseEvent('1', '2');
      evt.removeEventListener(MyObject.prototype.myListener);

  Source: Core/Event.js, line 32

### Members

#### numberOfListeners :Number

  The number of listeners currently subscribed to the event.
  Source: Core/Event.js, line 45

### Methods

#### addEventListener(listener, scope) → Event~RemoveCallback

  Registers a callback function to be executed whenever the event is raised. An optional scope can be provided to serve as the `this` pointer in which the function will execute.

  Name | Type | Description
  --- | --- | ---
  `listener` | function | The function to be executed when the event is raised.
  `scope` | Object | optional An optional object scope to serve as the `this` pointer in which the listener function will execute.

  ##### Returns:

  A function that will remove this event listener when invoked.

  ##### See:

  - Event#raiseEvent
  - Event#removeEventListener
  Source: Core/Event.js, line 65

#### raiseEvent(arguments)

  Raises the event by calling each registered listener with all supplied arguments.

  Name | Type | Description
  --- | --- | ---
  `arguments` | * | This method takes any number of parameters and passes them through to the listener functions.

  ##### See:

  - Event#addEventListener
  - Event#removeEventListener
  Source: Core/Event.js, line 135

#### removeEventListener(listener, scope) → Boolean

  Unregisters a previously registered callback.

  Name | Type | Description
  --- | --- | ---
  `listener` | function | The function to be unregistered.
  `scope` | Object | optional The scope that was originally passed to addEventListener.

  ##### Returns:

  `true` if the listener was removed; `false` if the listener and scope are not registered with the event.

  ##### See:

  - Event#addEventListener
  - Event#raiseEvent
  Source: Core/Event.js, line 91

### Type Definitions

#### RemoveCallback()

  A function that removes a listener.
  Source: Core/Event.js, line 163