project/vue/6-列表渲染.md

#### v-for

```html
<ul id="example-1">
  <li v-for="item in items" :key="item.message">
    {{ item.message }}
  </li>
</ul>
```

```js
var example1 = new Vue({
  el: '#example-1',
  data: {
    items: [
      { message: 'Foo' },
      { message: 'Bar' }
    ]
  }
})
```

```html
<ul id="example-2">
  <li v-for="(item, index) in items">
    {{ parentMessage }} - {{ index }} - {{ item.message }}
  </li>
</ul>
```

```js
var example2 = new Vue({
  el: '#example-2',
  data: {
    parentMessage: 'Parent',
    items: [
      { message: 'Foo' },
      { message: 'Bar' }
    ]
  }
})
```

### v-for遍历一个对象的元素

```html
<ul id="v-for-object" class="demo">
  <li v-for="value in object">
    {{ value }}
  </li>
</ul>

<div v-for="(value, name) in object">
  {{ name }}: {{ value }}
</div>

<div v-for="(value, name, index) in object">
  {{ index }}. {{ name }}: {{ value }}
</div>

<div v-for="item in items" v-bind:key="item.id">
  <!-- 内容 -->
</div>
```

```js
new Vue({
  el: '#v-for-object',
  data: {
    object: {
      title: 'How to do lists in Vue',
      author: 'Jane Doe',
      publishedAt: '2016-04-10'
    }
  }
})
```

#### 显示过滤/排序后的结果

- 有时，我们想要显示一个数组经过过滤或排序后的版本，而不实际变更或重置原始数据。在这种情况下，可以创建一个计算属性，来返回过滤或排序后的数组。

```html
<li v-for="n in evenNumbers">{{ n }}</li>
```

```js
data: {
  numbers: [ 1, 2, 3, 4, 5 ]
},
computed: {
  evenNumbers: function () {
    return this.numbers.filter(function (number) {
      return number % 2 === 0
    })
  }
}
```

- 在计算属性不适用的情况下 (例如，在嵌套 `v-for` 循环中) 可以使用一个方法

```html
<ul v-for="set in sets">
  <li v-for="n in even(set)">{{ n }}</li>
</ul>
```

```js
data: {
  sets: [[ 1, 2, 3, 4, 5 ], [6, 7, 8, 9, 10]]
},
methods: {
  even: function (numbers) {
    return numbers.filter(function (number) {
      return number % 2 === 0
    })
  }
}
```

```html
<div>
  <span v-for="n in 10">{{ n }} </span>
</div>

<ul>
  <template v-for="item in items">
    <li>{{ item.msg }}</li>
    <li class="divider" role="presentation"></li>
  </template>
</ul>
```

#### v-for,v-if 一同使用

- 当它们处于同一节点，`v-for` 的优先级比 `v-if` 更高，这意味着 `v-if` 将分别重复运行于每个 `v-for` 循环中。当你只想为*部分*项渲染节点时，这种优先级的机制会十分有用。
- 

```html
<--代码将只渲染未完成的 todo-->
<li v-for="todo in todos" v-if="!todo.isComplete">
  {{ todo }}
</li>
<ul v-if="todos.length">
  <li v-for="todo in todos">
    {{ todo }}
  </li>
</ul>
<p v-else>No todos left!</p>
```

#### v-for在组件中

```html
<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>
    <li
      is="todo-item"
      v-for="(todo, index) in todos"
      v-bind:key="todo.id"
      v-bind:title="todo.title"
      v-on:remove="todos.splice(index, 1)"
    ></li>
  </ul>
</div>
```



```js
Vue.component('todo-item', {
  template: '\
    <li>\
      {{ title }}\
      <button v-on:click="$emit(\'remove\')">Remove</button>\
    </li>\
  ',
  props: ['title']
})

new Vue({
  el: '#todo-list-example',
  data: {
    newTodoText: '',
    todos: [
      {
        id: 1,
        title: 'Do the dishes',
      },
      {
        id: 2,
        title: 'Take out the trash',
      },
      {
        id: 3,
        title: 'Mow the lawn'
      }
    ],
    nextTodoId: 4
  },
  methods: {
    addNewTodo: function () {
      this.todos.push({
        id: this.nextTodoId++,
        title: this.newTodoText
      })
      this.newTodoText = ''
    }
  }
})
```