eventEmitter实现

没有做任何异常处理,简单模拟实现

• 事件对象的每一个事件都对应一个数组

/*__events = {"事件1":[cb1,cb2],"事件2":[cb3,cb4],"事件3":[...],"事件4":[...],};*/class E{__events = {};constructor(){}//注册监听回调on(type , callback){//已经有对应事件回调则加入数组if(this.__events[type]){this.__events[type].push(callback);return true;}else{//没有则放入新数组this.__events[type] = [callback];return false;}}// 触发事件emit(type, ...args){if(this.__events[type] && this.__events[type].length){this.__events[type].forEach(cb => {cb.call(this,args);});}}//取消事件对应回调off(type, callback){if(this.__events[type] && this.__events[type].length){this.__events[type] = this.__events[type].filter((cb)=>{return cb !== callback && cb.ref !== callback;})return true;}return false;}//注册一次once(type, callback){let once_func = function(...args){callback.call(this,...args);this.off(type,once_func);}//用于取消 off()once_func.ref = callback;this.on(type,once_func);}
}let obj = new E();function cb (data) { console.log(data);}
obj.on("f1",cb);
obj.off("f1",cb);
obj.emit("f1", 1,2,3,4,5);