var app = new Vue({
  el: "#app",
  data: {
    firstName: "xiao",
    lastName: "dongxier"
  },
  computed: {
    fullName: {
      get: function () {
        return this.firstName + " " + this.lastName;
      },
      set: function (val) {
        console.log(val);
        var arr = val.split(" ");
        this.firstName = arr[0];
        this.lastName = arr[1];
      }
    }
  }
});