Js：手写EventBus核心逻辑

  <script>

    // 类EventBus -> 事件总线对象
    class HYEventBus {
      constructor() {
        this.eventMap = {}
      }

      on(eventName, eventFn) {
        let eventFns = this.eventMap[eventName]
        if (!eventFns) {
          eventFns = []
          this.eventMap[eventName] = eventFns
        }
        eventFns.push(eventFn)
      }
      
      off(eventName, eventFn) {
        let eventFns = this.eventMap[eventName]
        if (!eventFns) return
        for (let i = 0; i < eventFns.length; i++) {
          const fn = eventFns[i]
          if (fn === eventFn) {
            eventFns.splice(i, 1)
            break
          }
        }

        // 如果eventFns已经清空了
        if (eventFns.length === 0) {
          delete this.eventMap[eventName]
        }
      }

      emit(eventName, ...args) {
        let eventFns = this.eventMap[eventName]
        if (!eventFns) return
        eventFns.forEach(fn => {
          fn(...args)
        })
      }
    }


    // 使用过程
    const eventBus = new HYEventBus()

    // aside.vue组件中监听事件
    eventBus.on("navclick", (name, age, height) => {
      console.log("navclick listener 01", name, age, height)
    })

    const click =  () => {
      console.log("navclick listener 02")
    }
    eventBus.on("navclick", click)

    setTimeout(() => {
      eventBus.off("navclick", click)
    }, 5000);

    eventBus.on("asideclick", () => {
      console.log("asideclick listener")
    })


    // nav.vue
    const navBtnEl = document.querySelector(".nav-btn")
    navBtnEl.onclick = function() {
      console.log("自己监听到")
      eventBus.emit("navclick", "why", 18, 1.88)
    }

  </script>