event bus for vue

event-bus.js

import Vue from "vue"
import * as constants from "./event-constant"
const eventMap = new Map()

const eventBus = {
  data() {
    return {
      eventMap,
      registerEvent: {

      }
    }
  },
  methods: {
    subscribe(event, callback) {
      if (!constants[event]) throw new TypeError(`expect define constant before subscribe`);
      if (!this.eventMap.has(event)) this.initEvent(event);
      this.eventMap.get(event).add(callback);
      callback(this.registerEvent['event']);
    },
    broadcast(event, value) {
      if (!constants[event]) throw new TypeError(`expect define constant before broadcast`);
      if (!this.eventMap.has(event)) this.initEvent(event)
      this.$set(this.registerEvent, event, value);
    },
    initEvent(event) {
      this.eventMap.set(event, new Set());
      this.$set(this.registerEvent, event, null);
      this.$on(event, value => {
        this.eventMap.get(event).forEach(callback => callback(value))
      })
      this.$watch(`registerEvent.${event}`, function(value) {
        this.$emit(event, value);
      })
    }
  }
}
export default new Vue(eventBus);