極簡版，方便自己理解

class EventHub {
      constructor() {
        this.events = {}
      }

      on(eventName, func) {
        if (!this.events[eventName]) {
          this.events[eventName] = []
        }
        this.events[eventName].push(func)
      }
      
      // 應(yīng)考慮異步的場(chǎng)景，可能要判斷一下是不是異步任務(wù)？？
      emit(eventName, params) {
        let funcList = this.events[eventName]
        if (Array.isArray(funcList) && funcList.length > 0) {
          funcList.map((func) => {
            func(params)
          })
        }
      }

      off(eventName) {
        delete this.events[eventName]
      }
}