vue中的Bus/总线/发布订阅/观察者模式

Vue.prototype.bus = new Vue();

    Vue.component("child",{
      template: '<div @click="handleClick">{{selfContent}}</div>',
      props: {
        content: String
      },
      data() {
        return {
          selfContent: this.content
        }
      },
      methods: {
        handleClick() {
          this.bus.$emit("change", this.selfContent);
        }
      },
      mounted() {
        this_ = this;
        console.log(this);
        this.bus.$on("change", function(value) {
          console.log("value:",value);
        });
      }
    });
    var app = new Vue({
      el: '#app',
      mounted() {
        this.bus.$on("change", function(value){
          console.log(value);
        })
      }
    });