查看“Vue3 循环语句”的源代码

{{DISPLAYTITLE:Vue3 循环语句}}[[Category:Vue 3 教程|9]]
== Vue.js 循环语句 ==

循环使用 v-for 指令。

v-for 指令需要以 '''site in sites''' 形式的特殊语法， sites 是源数据数组并且 site 是数组元素迭代的别名。

v-for 可以绑定数据到数组来渲染一个列表：

== v-for 实例 ==

<sample title="" desc="" lang="html" hererun="1">
<div id="app">

  <ol>

    <li v-for="site in sites">

      {{ site.text }}

    </li>

  </ol>

</div>

<script>

const app = {

  data() {

    return {

      sites: [

        { text: 'Google' },

        { text: 'xiaoBai' },

        { text: 'Taobao' }

      ]

    }

  }

}

Vue.createApp(app).mount('#app')

</script>

 </sample>
<run name=""> <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Vue 测试实例 - 小白教程(xiaobai.wang)</title>
<script src="https://cdn.staticfile.org/vue/3.2.36/vue.global.min.js"></script>
</head>
<body>
<div id="app">
  <ol>
    <li v-for="site in sites">
      {{ site.text }}
    </li>
  </ol>
</div>
<script>
const app = {
  data() {
    return {
      sites: [
        { text: 'Google' },
        { text: 'xiaoBai' },
        { text: 'Taobao' }
      ]
    }
  }
}

Vue.createApp(app).mount('#app')
</script>
</body>
</html> </run>
v-for 还支持一个可选的第二个参数，参数值为当前项的索引：

== v-for 实例 ==

index 为列表项的索引值：

<sample title="" desc="" lang="html" hererun="1">
<div id="app">

  <ol>

    <li v-for="(site, index) in sites">

      {{ index }} -{{ site.text }}

    </li>

  </ol>

</div>

<script>

const app = {

  data() {

    return {

      sites: [

        { text: 'Google' },

        { text: 'xiaoBai' },

        { text: 'Taobao' }

      ]

    }

  }

}

Vue.createApp(app).mount('#app')

</script>

 </sample>
<run name=""> <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Vue 测试实例 - 小白教程(xiaobai.wang)</title>
<script src="https://unpkg.com/vue@next"></script>
</head>
<body>
<div id="app">
  <ol>
    <li v-for="(site, index) in sites">
      {{ index }} -{{ site.text }}
    </li>
  </ol>
</div>
<script>
const app = {
  data() {
    return {
      sites: [
        { text: 'Google' },
        { text: 'xiaoBai' },
        { text: 'Taobao' }
      ]
    }
  }
}

Vue.createApp(app).mount('#app')
</script>
</body>
</html> </run>
模板 &lt;template&gt; 中使用 v-for：

== v-for ==

<sample title="" desc="" lang="html" hererun="1">
<ul>
  <template v-for="site in sites">
    <li>{{ site.text }}</li>
    <li>--------------</li>
  </template>
</ul>
 </sample>
<run name=""> <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Vue 测试实例 - 小白教程(xiaobai.wang)</title>
<script src="https://unpkg.com/vue@next"></script>
</head>
<body>
<div id="app">
    <ul>
      <template v-for="site in sites">
        <li>{{ site.text }}</li>
        <li>--------------</li>
      </template>
    </ul>
</div>
<script>
const app = {
  data() {
    return {
      sites: [
        { text: 'Google' },
        { text: 'xiaoBai' },
        { text: 'Taobao' }
      ]
    }
  }
}

Vue.createApp(app).mount('#app')
</script>
</body>
</html> </run>

=== v-for 迭代对象 ===

v-for 可以通过一个对象的属性来迭代数据：

== v-for ==

<sample title="" desc="" lang="html" hererun="1">
<div id="app">
  <ul>
    <li v-for="value in object">
    {{ value }}
    </li>
  </ul>
</div>

<script>
const app = {
  data() {
    return {
      object: {
        name: '小白教程',
        url: 'http://www.xiaobai.wang',
        slogan: '学习使人快乐！'
      }
    }
  }
}

Vue.createApp(app).mount('#app')
</script>
 </sample>
<run name=""> <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Vue 测试实例 - 小白教程(xiaobai.wang)</title>
<script src="https://unpkg.com/vue@next"></script>
</head>
<body>
<div id="app">
  <ul>
    <li v-for="value in object">
    {{ value }}
    </li>
  </ul>
</div>

<script>
const app = {
  data() {
    return {
      object: {
        name: '小白教程',
        url: 'http://www.xiaobai.wang',
        slogan: '学习使人快乐！'
      }
    }
  }
}

Vue.createApp(app).mount('#app')
</script>
</body>
</html> </run>
你也可以提供第二个的参数为键名：

== v-for ==

<sample title="" desc="" lang="html" hererun="1">
<div id="app">
  <ul>
    <li v-for="(value, key) in object">
    {{ key }} : {{ value }}
    </li>
  </ul>
</div>
 </sample>
<run name=""> <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Vue 测试实例 - 小白教程(xiaobai.wang)</title>
<script src="https://unpkg.com/vue@next"></script>
</head>
<body>
<div id="app">
  <ul>
    <li v-for="(value, key) in object">
    {{ key }} : {{ value }}
    </li>
  </ul>
</div>

<script>
const app = {
  data() {
    return {
      object: {
        name: '小白教程',
        url: 'http://www.xiaobai.wang',
        slogan: '学习使人快乐！'
      }
    }
  }
}

Vue.createApp(app).mount('#app')
</script>
</body>
</html> </run>
第三个参数为索引：

== v-for ==

<sample title="" desc="" lang="html" hererun="1">
<div id="app">
  <ul>
    <li v-for="(value, key, index) in object">
     {{ index }}. {{ key }} : {{ value }}
    </li>
  </ul>
</div>
 </sample>
<run name=""> <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Vue 测试实例 - 小白教程(xiaobai.wang)</title>
<script src="https://unpkg.com/vue@next"></script>
</head>
<body>
<div id="app">
  <ul>
    <li v-for="(value, key, index) in object">
     {{ index }}. {{ key }} : {{ value }}
    </li>
  </ul>
</div>

<script>
const app = {
  data() {
    return {
      object: {
        name: '小白教程',
        url: 'http://www.xiaobai.wang',
        slogan: '学习使人快乐！'
      }
    }
  }
}

Vue.createApp(app).mount('#app')
</script>
</body>
</html> </run>

=== v-for 迭代整数 ===

v-for 也可以循环整数

== v-for ==

<sample title="" desc="" lang="html" hererun="1">
<div id="app">
  <ul>
    <li v-for="n in 10">
     {{ n }}
    </li>
  </ul>
</div>
 </sample>
<run name=""> <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Vue 测试实例 - 小白教程(xiaobai.wang)</title>
<script src="https://unpkg.com/vue@next"></script>
</head>
<body>
<div id="app">
  <ul>
    <li v-for="n in 10">
     {{ n }}
    </li>
  </ul>
</div>

<script>
    Vue.createApp(app).mount('#app')
</script>
</body>
</html> </run>

== 显示过滤/排序后的结果 ==

我们可以对数组的元素进行处理后再显示出来，一般可以通过创建一个计算属性，来返回过滤或排序后的数组。

== v-for 实例 ==

输出数组中的偶数：

<sample title="" desc="" lang="html" hererun="1">
<div id="app">
  <ul>
    <li v-for="n in evenNumbers">{{ n }}</li>
  </ul>
</div>
 </sample>
<run name=""> <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Vue 测试实例 - 小白教程(xiaobai.wang)</title>
<script src="https://unpkg.com/vue@next"></script>
</head>
<body>
<div id="app">
  <ul>
    <li v-for="n in evenNumbers">{{ n }}</li>
  </ul>
</div>

<script>
const app = {
    data() {
        return {
            numbers: [ 1, 2, 3, 4, 5 ]
         }
    },
    computed: {
        evenNumbers() {
            return this.numbers.filter(number => number % 2 === 0)
        }
    }
}

Vue.createApp(app).mount('#app')
</script>
</body>
</html> </run>

=== v-for/v-if 联合使用 ===

以上实例联合使用 v-for/v-if 给 select 设置默认值：

== v-for/v-if 实例 ==

v-for 循环出列表，v-if 设置选中值：

<sample title="" desc="" lang="html" hererun="1">
<div id="app">
   <select @change="changeVal($event)" v-model="selOption">
      <template v-for="(site,index) in sites" :site="site" :index="index" :key="site.id">
         <!-- 索引为 1 的设为默认值，索引值从0 开始-->
         <option v-if = "index == 1" :value="site.name" selected>{{site.name}}</option>
         <option v-else :value="site.name">{{site.name}}</option>
      </template>
   </select>
   <div>您选中了:{{selOption}}</div>
</div>

<script>
const app = {
    data() {
        return {
            selOption: "xiaoBai",
            sites: [
                  {id:1,name:"Google"},
                  {id:2,name:"xiaoBai"},
                  {id:3,name:"Taobao"},
            ]
         }

    },
    methods:{
        changeVal:function(event){
            this.selOption = event.target.value;
            alert("你选中了"+this.selOption);
        }
    }
}

Vue.createApp(app).mount('#app')
</script>
 </sample>
<run name=""> <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Vue 测试实例 - 小白教程(xiaobai.wang)</title>
<script src="https://unpkg.com/vue@next"></script>
</head>
<body>
<div id="app">
   <select @change="changeVal($event)" v-model="selOption">
      <template v-for="(site,index) in sites" :site="site" :index="index" :key="site.id">
         <!-- 索引为 1 的设为默认值，索引值从0 开始-->
         <option v-if = "index == 1" :value="site.name" selected>{{site.name}}</option>
         <option v-else :value="site.name">{{site.name}}</option>
      </template>
   </select>
   <div>您选中了:{{selOption}}</div>
</div>

<script>
const app = {
    data() {
        return {
            selOption: "xiaoBai",
            sites: [
                  {id:1,name:"Google"},
                  {id:2,name:"xiaoBai"},
                  {id:3,name:"Taobao"},
            ]
         }

    },
    methods:{
        changeVal:function(event){
            this.selOption = event.target.value;
            alert("你选中了"+this.selOption);
        }
    }
}

Vue.createApp(app).mount('#app')
</script>
</body>
</html> </run>

== 在组件上使用 v-for ==

如果你还没了解组件的内容，可以先跳过这部分。

在自定义组件上，你可以像在任何普通元素上一样使用 v-for：

<pre>&lt;my-component v-for=&quot;item in items&quot; :key=&quot;item.id&quot;&gt;&lt;/my-component&gt;</pre>
然而，任何数据都不会被自动传递到组件里，因为组件有自己独立的作用域。为了把迭代数据传递到组件里，我们要使用 props：

<pre>&lt;my-component
  v-for=&quot;(item, index) in items&quot;
  :item=&quot;item&quot;
  :index=&quot;index&quot;
  :key=&quot;item.id&quot;
&gt;&lt;/my-component&gt;</pre>
不自动将 item 注入到组件里的原因是，这会使得组件与 v-for 的运作紧密耦合。明确组件数据的来源能够使组件在其他场合重复使用。

下面是一个简单的 todo 列表的完整例子：

<sample title="" desc="" lang="html" hererun="1">
<div id="todo-list-example">
  <form v-on:submit.prevent="addNewTodo">
    <label for="new-todo">Add a todo</label>
    <input
      v-model="newTodoText"
      id="new-todo"
      placeholder="E.g. Feed the cat"
    />
    <button>Add</button>
  </form>
  <ul>
    <todo-item
      v-for="(todo, index) in todos"
      :key="todo.id"
      :title="todo.title"
      @remove="todos.splice(index, 1)"
    ></todo-item>
  </ul>
</div>
 </sample>
<run name=""> <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Vue 测试实例 - 小白教程(xiaobai.wang)</title>
<script src="https://unpkg.com/vue@next"></script>
</head>
<body>
<div id="todo-list-example">
  <form v-on:submit.prevent="addNewTodo">
    <label for="new-todo">添加 todo</label>
    <input
      v-model="newTodoText"
      id="new-todo"
      placeholder="例如：明天早上跑步"
    />
    <button>添加</button>
  </form>
  <ul>
    <todo-item
      v-for="(todo, index) in todos"
      :key="todo.id"
      :title="todo.title"
      @remove="todos.splice(index, 1)"
    ></todo-item>
  </ul>
</div>

<script>
const app = Vue.createApp({
  data() {
    return {
      newTodoText: '',
      todos: [
        {
          id: 1,
          title: '看电影'
        },
        {
          id: 2,
          title: '吃饭'
        },
        {
          id: 3,
          title: '上 XiaoBai.Wang 学习'
        }
      ],
      nextTodoId: 4
    }
  },
  methods: {
    addNewTodo() {
      this.todos.push({
        id: this.nextTodoId++,
        title: this.newTodoText
      })
      this.newTodoText = ''
    }
  }
})

app.component('todo-item', {
  template: `
    <li>
      {{ title }}
      <button @click="$emit('remove')">删除</button>
    </li>
  `,
  props: ['title'],
  emits: ['remove']
})

app.mount('#todo-list-example')
</script>
</body>
</html> </run>