new Vue({
        el:"#div",
        data:{
          arr:[1,2,3]
        }
      }).$watch("arr",function () {
        alert("数据改变了")
      })

<div id="div">
<input type="button" value="改变" @click="arr.push(5)">
<h1>
  {{arr}}
</h1>
</div>

 a{
      text-decoration: none;
      color: black;
    }
    #div{
      text-align: center;
      padding-top: 50px;
    }
    input{
      height: 25px;
      width: 500px;
      border-radius: 5px;
      outline: none;
    }
    ul{
      margin-left:470px;
      margin-top: 0;
    }
    li{
      height: 25px;
      text-align: left;
      border:1px solid gray;
      list-style: none;
      width: 500px;
    }

new Vue({
        el:"#div",
        data:{
          msg:" ",
          arr:[]
        },
        methods:{
          get:function () {
            this.$http.jsonp('https://sp0.baidu.com/5a1Fazu8AA54nxGko9WTAnF6hhy/su?',{
              wd:this.msg
            },{
              jsonp: 'cb'
            }).then(function(res){
              this.arr=res.data.s
            },function(s){
              console.log(s);
            });
          }
        }
      })

<div id="div">
<input type="text" v-model="msg" @keyup="get()">
<ul>
  <li v-for="item in arr"><a href="javascript:;" rel="external nofollow" >{{item}}</a></li>
</ul>
</div>