错误在 Vue 方法内部的回调中使用它

new Vue({
  el:"#app",
  data:{
    foo: "bar"
  },
  methods:{
    doSomethingAsynchronous(){
      setTimeout(function(){
        // This is wrong! Inside this function,
        // "this" refers to the window object.
        this.foo = "baz";
      }, 1000);
    }
  }
})