VUE の計算されたプロパティとリスナーの使用例

<div id="example">
  {{ message.split(&#39;&#39;).reverse().join(&#39;&#39;) }}
</div>

<div id="example">
  <p>Original message: "{{ message }}"</p>
  <p>Computed reversed message: "{{ reversedMessage }}"</p>
</div>
var vm = new Vue({
  el: &#39;#example&#39;,
  data: {
    message: &#39;Hello&#39;
  },
  computed: {
    // 计算属性的 getter
    reversedMessage: function () {
      // `this` 指向 vm 实例      return this.message.split(&#39;&#39;).reverse().join(&#39;&#39;)
    }
  }
})
Original message: "Hello"
Computed reversed message: "olleH"

<p>Reversed message: "{{ reversedMessage() }}"</p>
// 在组件中
methods: {
  reversedMessage: function () {    return this.message.split(&#39;&#39;).reverse().join(&#39;&#39;)
  }
}

computed: {
  now: function () {    return Date.now()
  }
}

<div id="demo">{{ fullName }}</div>
var vm = new Vue({
  el: &#39;#demo&#39;,
  data: {
    firstName: &#39;Foo&#39;,
    lastName: &#39;Bar&#39;,
    fullName: &#39;Foo Bar&#39;
  },
  watch: {
    firstName: function (val) {
      this.fullName = val + &#39; &#39; + this.lastName
    },
    lastName: function (val) {
      this.fullName = this.firstName + &#39; &#39; + val
    }
  }
})

var vm = new Vue({
  el: '#demo',
  data: {
    firstName: 'Foo',
    lastName: 'Bar'
  },
  computed: {
    fullName: function () {      return this.firstName + ' ' + this.lastName
    }
  }
})

// ...
computed: {
  fullName: {
    // getter
    get: function () {      return this.firstName + ' ' + this.lastName
    },
    // setter
    set: function (newValue) {
      var names = newValue.split(' ')
      this.firstName = names[0]
      this.lastName = names[names.length - 1]
    }
  }
}
// ...

<div id="watch-example">
  <p>
    Ask a yes/no question:
    <input v-model="question">
  </p>
  <p>{{ answer }}</p>
</div>
<!-- 因为 AJAX 库和通用工具的生态已经相当丰富，Vue 核心代码没有重复 -->
<!-- 提供这些功能以保持精简。这也可以让你自由选择自己更熟悉的工具。 -->
<script src="https://cdn.jsdelivr.net/npm/axios@0.12.0/dist/axios.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/lodash@4.13.1/lodash.min.js"></script>
<script>
var watchExampleVM = new Vue({
  el: &#39;#watch-example&#39;,
  data: {
    question: &#39;&#39;,
    answer: &#39;I cannot give you an answer until you ask a question!&#39;
  },
  watch: {
    // 如果 `question` 发生改变，这个函数就会运行
    question: function (newQuestion, oldQuestion) {
      this.answer = &#39;Waiting for you to stop typing...&#39;
      this.getAnswer()
    }
  },
  methods: {
    // `_.debounce` 是一个通过 Lodash 限制操作频率的函数。
    // 在这个例子中，我们希望限制访问 yesno.wtf/api 的频率
    // AJAX 请求直到用户输入完毕才会发出。想要了解更多关于
    // `_.debounce` 函数 (及其近亲 `_.throttle`) 的知识，
    // 请参考：https://lodash.com/docs#debounce
    getAnswer: _.debounce(
      function () {        if (this.question.indexOf(&#39;?&#39;) === -1) {
          this.answer = &#39;Questions usually contain a question mark. ;-)&#39;
          return
        }
        this.answer = &#39;Thinking...&#39;
        var vm = this
        axios.get(&#39;https://yesno.wtf/api&#39;)
          .then(function (response) {
            vm.answer = _.capitalize(response.data.answer)
          })
          .catch(function (error) {
            vm.answer = &#39;Error! Could not reach the API. &#39; + error
          })
      },
      // 这是我们为判定用户停止输入等待的毫秒数      500
    )
  }
})
</script>