SOURCE

var vm = new Vue({
  el:'#watch-example',
  data:{
    question: '',
    answer: 'I cannot give you an answer until you ask a question!'
  },
  watch:{
    question:function(newQuestion,oldQuestion){
      this.question='Waiting for you to stop typing...'
      this.getAnswer()
    }
  },
  methods:{
    getAnswer: _.debounce(
      function(){
         if (this.question.indexOf('?') === -1) {
          this.answer = 'Questions usually contain a question mark. ;-)'
          return
        }
        this.answer = 'Thinking...'
        var vm = this
       axios.get('https://yesno.wtf/api')
          .then(function (response) {
            vm.answer = _.capitalize(response.data.answer)
          })
          .catch(function (error) {
            vm.answer = 'Error! Could not reach the API. ' + error
          })
      }
    }
      ,
      // 这是我们为判定用户停止输入等待的毫秒数
      500
    )
  }
})

<div id="watch-example">
  <p>
    Ask a yes/no question:
    <input v-model="question">
  </p>
  <p>{{ answer }}</p>
</div>