class EventEmitter {
// 补全代码
constructor(){
this.obj={}
}
on(name,fn){
let result = this.obj;
if(!result[name]){
result[name] = [fn]
}else{
result[name].push(fn)
}
}//不能用逗号
emit(name){
let result = this.obj;
if(result[name]){
for(let fun of result[name]){
fun([].slice.call(arguments,1));
}
}
}
}