messaging/Event.js
/**
		 * Registers an event handler which will receive a notification when
		 * {@link Event#fire} is called.
		 *
		 * @public
		 * @param {Function} handler - The function which will be called each time the event fires. The first argument will be the event data. The second argument will be the event owner (i.e. sender).
		 * @returns {Disposable}
		 */
Registers an event handler which will receive a notification when
Event#fire is called.

@public
@param {Function} handler - The function which will be called each time the event fires. The first argument will be the event data. The second argument will be the event owner .
@returns {Disposable}
Registers an event handler which will receive a notification when Event#fire is called . @public @param { Function } handler - The function which will be called each time the event fires . The first argument will be the event data . The second argument will be the event owner . @returns { Disposable }
register(handler) {
			assert.argumentIsRequired(handler, 'handler', Function);
			addRegistration.call(this, handler);
			return Disposable.fromAction(() => {
				if (this.getIsDisposed()) {
					return;
				}
				removeRegistration.call(this, handler);
			});
		}
register ( handler ) { assert . argumentIsRequired ( handler , 'handler' , Function ) ; addRegistration . call ( this , handler ) ; return Disposable . fromAction ( ( ) => { if ( this . getIsDisposed ( ) ) { return ; } removeRegistration . call ( this , handler ) ; } ) ; }
Registers an event handler which will receive a notification when
 {@link Event#fire} is called.
Registers an event handler which will receive a notification when { @link Event#fire } is called .