function Eventdispatcher() {}
Object.assign( Eventdispatcher.prototype, {
addEventListener: function ( type, listener ) {
if ( this._listeners === undefined ) this._listeners = {};
var listeners = this._listeners;
if ( listeners[ type ] === undefined ) {
listeners[ type ] = [];
}
if ( listeners[ type ].indexOf( listener ) === - 1 ) {
listeners[ type ].push( listener );
}
},
hasEventListener: function ( type, listener ) {
if ( this._listeners === undefined ) return false;
var listeners = this._listeners;
return listeners[ type ] !== undefined && listeners[ type ].indexOf( listener ) !== - 1;
},
removeEventListener: function ( type, listener ) {
if ( this._listeners === undefined ) return;
var listeners = this._listeners;
var listenerArray = listeners[ type ];
if ( listenerArray !== undefined ) {
var index = listenerArray.indexOf( listener );
if ( index !== - 1 ) {
listenerArray.splice( index, 1 );
}
}
},
dispatchEvent: function ( event ) {
if ( this._listeners === undefined ) return;
var listeners = this._listeners;
var listenerArray = listeners[ event.type ];
if ( listenerArray !== undefined ) {
event.target = this;
var array = listenerArray.slice( 0 );
for ( var i = 0, l = array.length; i < l; i ++ ) {
array[ i ].call( this, event );
}
}
}
} );
var pac=new Eventdispatcher();
var mm=null;
pac.addEventListener("xuhaitao",function(){
mm=this;
console.log(this,"wo zi ji");
})
var nn=null;
pac.addEventListener("xuhaitao",function(){
nn=this;
console.log(this,"wo di di");
})
pac.dispatchEvent({type:"xuhaitao"})
console.log(mm===nn);
两个this都指向pac实例对象
