简单事件监听实现逻辑

class EventBus {
    constructor () {
      this.event = {}
  }
  on (type, listener, ...agrs) {
      this.event[type] = this.event[type] || []
    listener.agrs = [...agrs] // 将参数放到监听函数的属性中
    this.event[type].push(listener)
    return this.off.bind(listener) // 同步绑定off函数
  }
  off (type, listener) {
      this.event[type] = this.event[type].filter((type) => type !== listener) // 解绑函数
  }
  fire(type, ...args) {
      if (this.event[type]) {
        this.event[type].forEach((listener) => {
          let allArgs = [...agrs, ...listener.agrs]
        listener.call(this, ...allArgs)
      })
    }
  }
  once (type, listener) {
       this.events[type] = this.events[type] || [];
     function proxyFun(...agrs) {
             listener.call(this, ...agrs)
        this.off(type, listener)
     }
     this.event[type].push(proxyFun)
  }
}