bus.js

function Bus () {
  this.events = {}
  this.on = async (eventName, handler) => {
    if (!this.events[eventName]) {
      this.events[eventName] = []
    }
    let targetHandler = handler
    let before = []
    if (typeof handler === 'function') {
      position = this.events[eventName].length
    } else if (handler.before instanceof Array) {
      // 找到 before 中最先前的 idx
      let position = this.events.length
      targetHandler = handler.fn
      before = handler.before
      handler.before.map(bf => {
        for (let i in this.events[eventName]) {
          if (this.events[eventName].name === bf) {
            if (position > i) {
              position = i
            }
          }
        }
      })
    }
    this.events[eventName].splice(position, 0, {
      handler: targetHandler,
      before: [],
      stack: []
    })
    return this.events[eventName][position].stack
  }

  const executer = async (fn, args, en) => {
    await fn(...args)
    return 'in ' + en
  }

  this.trigger = async function (eventName, ...args) {
    if (this.events[eventName] && this.events[eventName] instanceof Array) {
      for (let i in this.events[eventName]) {
        let listener = this.events[eventName][i]
        let r = await executer(listener.handler, args, eventName)
        console.log('===caller', arguments.caller)
        listener.stack.push(r)
      }
    }
  }
}