示例

使用v-if指令创建一个<div>如果条件为“真”，则为元素。

<div v-if="createImgDiv">
  <img src="/img_apple.svg" alt="apple">
  <p>This is an apple.</p>
</div>

示例1

使用v-if以数据属性作为条件表达式，以及v-else。

示例2

使用v-if以比较检查作为条件表达式，以及v-else。

示例3

使用v-if和...一起v-else-if和v-else根据存储的打字机数量显示状态消息。

示例4

使用v-if使用原生 JavaScript 方法作为条件表达式，以及v-else。

示例5

使用v-if渲染一个<div>从 API 接收数据时标记。

<template>
  <h1>Example</h1>
  <p>Click the button to fetch data with an HTTP request.</p>
  <p>Each click generates an object with a random user from <a href="https://random-data-api.com/" target="_blank">https://random-data-api.com/</a>.</p>
  <p>The robot avatars are lovingly delivered by <a href="http://Robohash.org" target="_blank">RoboHash</a>.</p>
  <button @click="fetchData">Fetch data</button>
  <div v-if="data" id="dataDiv">
    <img :src="data.avatar" alt="avatar">
    <pre>{{ data.first_name + " " + data.last_name }}</pre>
    <p>"{{ data.employment.title }}"</p>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        data: null,
      };
    },
    methods: {
      async fetchData() {      
        const response = await fetch("https://random-data-api.com/api/v2/users"); 
        this.data = await response.json();
      },    
    }
  };
</script>

<style>
#dataDiv {
  width: 240px;
  background-color: aquamarine;
  border: solid black 1px;
  margin-top: 10px;
  padding: 10px;
}
#dataDiv > img {
  width: 100%;
}
pre {
  font-size: larger;
  font-weight: bold;
}
</style>

示例6

使用v-if创建一个组件，以便mounted生命周期钩子被触发。

CompOne.vue:

<template>
    <h2>Component</h2>
    <p>Right after this component is added to the DOM, the mounted() function is called and we can add code to that mounted() function. In this example, an alert popup box appears after this component is mounted.</p>
    <p><strong>Note:</strong> The reason that the alert is visible before the component is visible is because the alert is called before the browser gets to render the component to the screen.</p>
  </template>
  
  <script>
  export default {
    mounted() {
      alert("The component is mounted!");
    }
  }
  </script>

App.vue:

<template>
  <h1>The 'mounted' Lifecycle Hook</h1>
  <button @click="this.activeComp = !this.activeComp">Create component</button>
  <div>
    <comp-one v-if="activeComp"></comp-one>
  </div>
</template>

<script>
export default {
  data() {
    return {
      activeComp: false
    }
  }
}
</script>

<style scoped>
  div {
    border: dashed black 1px;
    border-radius: 10px;
    padding: 20px;
    margin: 10px;
    width: 400px;
    background-color: lightgreen;
  }
</style>

示例7

使用v-if切换<p>元素以便触发动画。

<template>
  <h1>Add/Remove <p> Tag</h1>
  <button @click="this.exists = !this.exists">{{btnText}}</button><br>
  <Transition>
    <p v-if="exists">Hello World!</p>
  </Transition>
</template>

<script>
export default {
  data() {
    return {
      exists: false
    }
  },
  computed: {
    btnText() {
      if(this.exists) {
        return 'Remove';
      }
      else {
        return 'Add';
      }
    }
  }
}
</script>

<style scoped>
  .v-enter-from {
    opacity: 0;
    translate: -100px 0;
  }
  .v-enter-to {
    opacity: 1;
    translate: 0 0;
  }
  .v-leave-from {
    opacity: 1;
    translate: 0 0;
  }
  .v-leave-to {
    opacity: 0;
    translate: 100px 0;
  }
  p {
    background-color: lightgreen;
    display: inline-block;
    padding: 10px;
    transition: all 0.5s;
  }
</style>