three
Version:
JavaScript 3D library
132 lines (89 loc) • 2.74 kB
JavaScript
/**
* This modules allows to dispatch event objects on custom JavaScript objects.
*
* Main repository: [eventdispatcher.js]{@link https://github.com/mrdoob/eventdispatcher.js/}
*
* Code Example:
* ```js
* class Car extends EventDispatcher {
* start() {
* this.dispatchEvent( { type: 'start', message: 'vroom vroom!' } );
* }
*};
*
* // Using events with the custom object
* const car = new Car();
* car.addEventListener( 'start', function ( event ) {
* alert( event.message );
* } );
*
* car.start();
* ```
*/
class EventDispatcher {
/**
* Adds the given event listener to the given event type.
*
* @param {string} type - The type of event to listen to.
* @param {Function} listener - The function that gets called when the event is fired.
*/
addEventListener( type, listener ) {
if ( this._listeners === undefined ) this._listeners = {};
const listeners = this._listeners;
if ( listeners[ type ] === undefined ) {
listeners[ type ] = [];
}
if ( listeners[ type ].indexOf( listener ) === - 1 ) {
listeners[ type ].push( listener );
}
}
/**
* Returns `true` if the given event listener has been added to the given event type.
*
* @param {string} type - The type of event.
* @param {Function} listener - The listener to check.
* @return {boolean} Whether the given event listener has been added to the given event type.
*/
hasEventListener( type, listener ) {
const listeners = this._listeners;
if ( listeners === undefined ) return false;
return listeners[ type ] !== undefined && listeners[ type ].indexOf( listener ) !== - 1;
}
/**
* Removes the given event listener from the given event type.
*
* @param {string} type - The type of event.
* @param {Function} listener - The listener to remove.
*/
removeEventListener( type, listener ) {
const listeners = this._listeners;
if ( listeners === undefined ) return;
const listenerArray = listeners[ type ];
if ( listenerArray !== undefined ) {
const index = listenerArray.indexOf( listener );
if ( index !== - 1 ) {
listenerArray.splice( index, 1 );
}
}
}
/**
* Dispatches an event object.
*
* @param {Object} event - The event that gets fired.
*/
dispatchEvent( event ) {
const listeners = this._listeners;
if ( listeners === undefined ) return;
const listenerArray = listeners[ event.type ];
if ( listenerArray !== undefined ) {
event.target = this;
// Make a copy, in case listeners are removed while iterating.
const array = listenerArray.slice( 0 );
for ( let i = 0, l = array.length; i < l; i ++ ) {
array[ i ].call( this, event );
}
event.target = null;
}
}
}
export { EventDispatcher };