Understand common instructions in vue.js (summary)

v-text

v-text is mainly used to update textContent, which can be equivalent to the text attribute of JS.

<span v-text="text"></span>
// 等同于下方语句： 
<span>{{text}}</span>

v-html

The double brace method will interpret the data as plain text, not HTML. In order to output real HTML, you can use the v-html command. It is equivalent to JS's innerHtml property.

Note: Content is inserted as normal HTML - will not be compiled as a Vue template.

<div v-html="html"></div>

v-show

Equivalent to css's dispaly attribute switching between "none" and "block" settings.

<div v-show="isShow">hello world</div>

v-if

v-if can implement conditional rendering. Vue will render elements based on the true and false conditions of the expression value. .

<div v-show="isShow">hello world</div>

The above code, if isShow is false, the div is rendered, otherwise it is not rendered.

Note:

v-if needs to be distinguished from v-show. The elements of v-show will always be rendered and saved in the dom. It just simply switches the dispaly attribute of css.

v-if has higher switching overhead.

v-show has higher initial rendering overhead.

So, if you want to switch very frequently, it is better to use v-show; if the conditions are unlikely to change during runtime, it is better to use v-if.

v-else

v-else is used with v-if, it must follow v-if or v-else -if after, otherwise it has no effect.
Similar to JS’s if .. else.

<div v-if="isSow">值为true的时候显示的内容</div>
<div v-else>值为false的时候显示的内容</div>

v-else-if

v-else-if acts as the else-if block of v-if and can be used in a chain repeatedly. Similar to JS's if .. else if .. else

<div v-if="type===&#39;A&#39;">
  A
</div>
<div v-if="type===&#39;B&#39;">
  B
</div>
<div v-if="type===&#39;C&#39;">
  C
</div>
<div v-else>
  Not A,B,C
</div>

v-for

Use the v-for instruction to render by traversing the array .

<ul>
	<li v-for="item in items">{{item.name}}</li>
</ul>

<script>
new Vue({
  el: &#39;#app&#39;,
  data: {
    items: [
      { name: &#39;Runoob&#39; },
      { name: &#39;Google&#39; },
      { name: &#39;Taobao&#39; }
    ]
  }
})
</script>

// 补充：
// 也可以自行指定参数，最多可以接受3个参数
<div v-for="(item, index) in items"></div>
<div v-for="(val, key) in object"></div>
<div v-for="(val, name, index) in object"></div>

// 迭代对象
<ul>
    <li v-for="value in object">
     {{ index }}. {{ key }} : {{ value }}
</li>

// 迭代整数
<ul>
    <li v-for="n in 10">
     {{ n }}
    </li>
</ul>

v-on

Bind event listener. The event type is specified by parameters. The expression can be the name of a method or an inline statement, and can be omitted if there are no modifiers.
v-on can also be abbreviated as "@", such as:

v-on="show" can be abbreviated as: @show

<!-- 方法处理器 -->
<button v-on:click="doThis"></button>

<!-- 动态事件 (2.6.0+) -->
<button v-on:[event]="doThis"></button>

<!-- 内联语句 -->
<button v-on:click="doThat(&#39;hello&#39;, $event)"></button>

<!-- 缩写 -->
<button @click="doThis"></button>

<!-- 动态事件缩写 (2.6.0+) -->
<button @[event]="doThis"></button>

<!-- 停止冒泡 -->
<button @click.stop="doThis"></button>

<!-- 阻止默认行为 -->
<button @click.prevent="doThis"></button>

<!-- 阻止默认行为，没有表达式 -->
<form @submit.prevent></form>

<!--  串联修饰符 -->
<button @click.stop.prevent="doThis"></button>

<!-- 键修饰符，键别名 -->
<input @keyup.enter="onEnter">

<!-- 键修饰符，键代码 -->
<input @keyup.13="onEnter">

<!-- 点击回调只会触发一次 -->
<button v-on:click.once="doThis"></button>

<!-- 对象语法 (2.4.0+) -->
<button v-on="{ mousedown: doThis, mouseup: doThat }"></button>

You can also use modifiers, as follows :

.stop - Call event.stopPropagation().

.prevent - Calls event.preventDefault().

.capture - Use capture mode when adding event listeners.

.self - The callback is only triggered when the event is triggered from the element itself to which the listener is bound.

.{keyCode | keyAlias} - The callback is only fired when the event is triggered from a specific key.

.native - Listen to native events on the root element of the component.

.once - The callback is triggered only once.

.left - only fires when the left mouse button is clicked.

.right - only triggered when the right mouse button is clicked.

.middle - only triggered when the middle mouse button is clicked.

.passive - add a listener in { passive: true } mode

v-bind

Dynamically bind one or more attributes, or a component prop to an expression. Often used to dynamically bind classes and styles. And href etc.

can be abbreviated as: " : ", such as:

v-bind:class=" isActive : 'active' :' ' ", can be abbreviated as: :class=" isActive : ' active' :' ' "

<div v-bind:class=" isActive : &#39;active&#39; :&#39; &#39; "></div>
<script>
  var app = new Vue({
    el: &#39;#app&#39;,
    data: {
      isActive : true, 
    }
  })
</script>

//渲染结果为： <div class="active"></div>

Bind multiple classes, the details are as follows:

<div v-bind:class="[ isActive : &#39;active&#39; :&#39; &#39; , isError: &#39;error&#39; :&#39; &#39; ]">
</div>
<script>
  var app = new Vue({
    el: &#39;#app&#39;,
    data: {
      isActive : true, 
      isError:  true,
    }
  })
</script>

//渲染结果为： <div class="active error"></div>

Other examples, see the code below for details:

<!-- 绑定一个属性 -->
<img v-bind:src="imageSrc">

<!-- 动态特性名 (2.6.0+) -->
<button v-bind:[key]="value"></button>

<!-- 缩写 -->
<img :src="imageSrc">

<!-- 动态特性名缩写 (2.6.0+) -->
<button :[key]="value"></button>

<!-- 内联字符串拼接 -->
<img :src="&#39;/path/to/images/&#39; + fileName">

<!-- class 绑定 -->
<div :class="{ red: isRed }"></div>
<div :class="[classA, classB]"></div>
<div :class="[classA, { classB: isB, classC: isC }]">

<!-- style 绑定 -->
<div :style="{ fontSize: size + &#39;px&#39; }"></div>
<div :style="[styleObjectA, styleObjectB]"></div>

<!-- 绑定一个有属性的对象 -->
<div v-bind="{ id: someProp, &#39;other-attr&#39;: otherProp }"></div>

<!-- 通过 prop 修饰符绑定 DOM 属性 -->
<div v-bind:text-content.prop="text"></div>

<!-- prop 绑定。“prop”必须在 my-component 中声明。-->
<my-component :prop="someThing"></my-component>

<!-- 通过 $props 将父组件的 props 一起传给子组件 -->
<child-component v-bind="$props"></child-component>

<!-- XLink -->
<svg><a :xlink:special="foo"></a></svg>

v-model

#Create two-way binding on a form control or component.
v-model will ignore the initial values ​​of the value, checked, and selected attributes of all form elements. Because it selects Vue instance data as the specific value.

<div id="app">
  <input v-model="somebody">
  <p>hello {{somebody}}</p>
</div>
<script>
  var app = new Vue({
    el: &#39;#app&#39;,
    data: {
      somebody:&#39;小明&#39;
    }
  })
</script>

In this example, enter another name directly into the browser input, and the content of the p below will change directly accordingly. This is two-way data binding.

Available modifiers:

.lazy - By default, v-model synchronizes the value and data of the input box. You can use this modifier to switch to resynchronization in the change event.

.number - Automatically convert the user's input value into a numerical type

.trim - Automatically filter the leading and trailing spaces entered by the user

How to use modifiers: For example:

<input v-model.trim="somebody">

v-pre

v-pre is mainly used to skip the compilation process of this element and its sub-elements. Can be used to display the original Mustache tag. Skip a large number of nodes without instructions to speed up compilation.

<div id="app">
  <span v-pre>{{message}}</span> //这条语句不进行编译
  <span>{{message}}</span>
</div>

This directive is used to remain on the element until the end of the associated instance for compilation.

<div id="app" v-cloak>
  <div>
    {{message}}
  </div>
</div>
<script type="text/javascript">
  new Vue({
   el:&#39;#app&#39;,
   data:{
    message:&#39;hello world&#39;
   }
  })
</script>

Explanation:
will flash when the page is loaded. It will first display:

<div>
  {{message}}
</div>

and then compile to:

<div>
  hello world!
</div>

The v-cloak command can To solve the problem of interpolation flickering above, as follows: In fact, what is used is to hide the content through the style attribute when the interpolation is not loaded.

  <style>
    [v-cloak] {
       display: none; 
    }
  </style>
  
  <div id="app">
    <!-- 使用 v-cloak 能够解决 插值表达式闪烁的问题 -->
    <p v-cloak>++++++++ {{ msg }} ----------</p>
  </div>
  
  <script>
    var vm = new Vue({
      el: &#39;#app&#39;,
      data: {
        msg: &#39;hello&#39;,
      }
    })
  </script>

v-once

v-once关联的实例，只会渲染一次。之后的重新渲染，实例极其所有的子节点将被视为静态内容跳过，这可以用于优化更新性能。

<span v-once>This will never change:{{msg}}</span> //单个元素
<div v-once>//有子元素
  <h1>comment</h1>
  <p>{{msg}}</p>
</div>
<my-component v-once:comment="msg"></my-component> //组件
<ul>
  <li v-for="i in list">{{i}}</li>
</ul>

上面的例子中，msg,list即使产生改变，也不会重新渲染。

v-slot

提供具名插槽或需要接收 prop 的插槽。

可简写为：#

slot 和 scope-slot 是在 vue@2.6.x 之前的语法，而从 vue@2.6.0 开始，官方推荐我们使用 v-slot 来替代前两者。

使用具名插槽来自定义模板内容（vue@2.6.x已经废弃）

<div class="container">
  <header>
    <slot name="header"></slot>
  </header>
  <main>
    <slot></slot>
  </main>
  <footer>
    <slot name="footer"></slot>
  </footer>
</div>

在向具名插槽提供内容的时候，我们可以在一个父组件的 元素上使用 slot 特性：

<base-layout>
  <template slot="header">
    <h1>Here might be a page title</h1>
  </template>

  <p>A paragraph for the main content.</p>
  <p>And another one.</p>

  <template slot="footer">
    <p>Here&#39;s some contact info</p>
  </template>
</base-layout>

接下来，使用 v-slot 指令改写上面的栗子：

<base-layout>
  <template v-slot:header>
    <h1>Here might be a page title</h1>
  </template>

  <p>A paragraph for the main content.</p>
  <p>And another one.</p>

  <template v-slot:footer>
    <p>Here&#39;s some contact info</p>
  </template>
</base-layout>

使用 # 简写代替 v-slot

<base-layout>
  <template #header>
    <h1>Here might be a page title</h1>
  </template>

  <p>A paragraph for the main content.</p>
  <p>And another one.</p>

  <template #footer>
    <p>Here&#39;s some contact info</p>
  </template>
</base-layout>

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