js实现emit的方法

class EventEmit{
  constructor(){
    this.events = []
  }
  on(type,listener){
    this.events[type]||(this.events[type]=[]).push(listener)
    console.log(this.events)
  }
  emit(type,...args){
    if(this.events[type]){
      this.events[type].forEach(fn=>{fn.call(type,...args)})
    }
  }
  off(type,listener){
    let index = this.events[type].indexOf(listener)
    this.events[type].splice(index,1)
  }
}

let event= new EventEmit()
event.on('say',function(str) {
  console.log(str);
});
event.emit('say','visa');