Analysis of v-model directive in Vue (with code)

The content of this article is about the analysis of the v-model instruction in Vue (with code). It has a good reference value and I hope it can help friends in need.

1. Instruction explanation

v-model creates a two-way binding on a form control or component, which is essentially responsible for monitoring user input events (onchange, onkeyup, onkeydown, etc., which one specifically , please also check the official underlying implementation documentation) to update the data and perform some special processing for some extreme scenarios.

2. Form input binding methods and methods

2.1 Input box implements two-way data binding example:

<template>
  <div>
    <p class="p1">{{title}}</p>
    <div class="spancss1">
      <label>请输入:</label><input type="text" v-model="inputs"/><br/>
      <label>你在input框中输入了:</label><span>{{inputs}}</span>
    </div>
  </div>
</template>

<script>
    export default {
        name:"v-model",
      data(){
          return {
            title: &#39;v-model学习&#39;,
            inputs: &#39;&#39;
          }
      }
    }
</script>

<style scoped>
  .p1{
  text-align: left;
  }
  .spancss1{
      float: left;
      }
</style>

2.2 Textarea multiple Example of double-thinking data binding using line text:

<template>
  <div>
    <p class="p1">{{title}}</p>
    <div class="spancss1">
      <label>请输入:</label><textarea v-model="text"></textarea><br/>
      <label>你在textarea框中输入了:</label><span>{{text}}</span>
    </div>
  </div>
</template>

<script>
  export default {
    name:"v-model",
    data(){
      return {
        title: &#39;v-model学习&#39;,
        text: &#39;&#39;
      }
    }
  }
</script>

<style scoped>
  .p1{
    text-align: left;
  }
  .spancss1{
    float: left;
  }
</style>

2.3 Check box data binding

Single check box data binding Example:

<template>
  <div>
    <p class="p1">{{title}}</p>
    <div class="spancss1">
      <label>请输入:</label><input type="checkbox" id="checkbox" v-model="checked">选我<br/>
      <label v-if="checked">选中了:</label>
      <label v-if="!checked">没选中:</label>
      <span>{{ checked }}</span>
    </div>
  </div>
</template>

<script>
  export default {
    name:"v-model",
    data(){
      return {
        title: &#39;v-model学习&#39;,
        checked: &#39;&#39;
      }
    }
  }
</script>

<style scoped>
  .p1{
    text-align: left;
  }
  .spancss1{
    float: left;
  }
</style>

Multiple check boxes to implement data binding Example:

<template>
  <div>
    <p class="p1">{{title}}</p>
    <div class="spancss1">
      <label>请输入:</label>
      <input type="checkbox" id="vue1" value="vue1" v-model="checkedValues">vue1
      <input type="checkbox" id="vue2" value="vue2" v-model="checkedValues">vue2
      <input type="checkbox" id="vue3" value="vue3" v-model="checkedValues">vue3
      <br/>
      <label>选中了：</label><span>{{ checkedValues }}</span>
    </div>
  </div>
</template>

<script>
  export default {
    name:"v-model",
    data(){
      return {
        title: &#39;v-model学习&#39;,
        checkedValues: []
      }
    }
  }
</script>

<style scoped>
  .p1{
    text-align: left;
  }
  .spancss1{
    float: left;
  }
</style>

2.4 Radio buttons implement data binding, and the selected radio button value is obtained and displayed:

<template>
  <div>
    <p class="p1">{{title}}</p>
    <div class="spancss1">
      <input type="radio" id="radio1" value="1" v-model="checked">男<br/>
      <input type="radio" id="radio2" value="2" v-model="checked">女<br/>
      <label> 选中了：{{ checked }}</label>
    </div>
  </div>
</template>

<script>
  export default {
    name:"v-model",
    data(){
      return {
        title: &#39;v-model学习&#39;,
        checked: &#39;&#39;
      }
    }
  }
</script>

<style scoped>
  .p1{
    text-align: left;
  }
  .spancss1{
    float: left;
  }
</style>

2.5 Introduction to the selection box

Method 1: The selection box implements two-way data binding. First, the selection box implements a single selection. When the options in the radio button box set the disabled attribute, the options cannot be selected. When When the options in the radio button box have no value, the text of the options will be bound when the options are selected. When the options in the radio button box have a value, the value of the options will be bound when the options are selected. The example is as follows:

<template>
  <div>
    <p class="p1">{{title}}</p>
    <div class="spancss1">
      <select v-model="selected">
        <option disabled value="">请选择</option>
        <option>A</option>
        <option value="2">B</option>
        <option value="3">C</option>
      </select>
      <span>Selected: {{ selected }}</span>
    </div>
  </div>
</template>

<script>
  export default {
    name:"v-model",
    data(){
      return {
        title: &#39;v-model学习&#39;,
        selected: &#39;&#39;
      }
    }
  }
</script>

<style scoped>
  .p1{
    text-align: left;
  }
  .spancss1{
    float: left;
  }
</style>

Method 2 introduces the situation of multiple selections in the selection box. First, you need to add the multiple attribute to the select. When the options are in the radio button When setting the disabled attribute, this option cannot be selected. When the options in the radio button box have no value, the text of this option will be bound when this option is selected. When the options in the radio button box have a value, when this option is selected, The value of this options will be bound, then press the ctrl key and click on the options to be selected. A simple example is as follows:

<template>
  <div>
    <p class="p1">{{title}}</p>
    <div class="spancss1">
      <select v-model="selected" multiple>
        <option disabled value="">请选择</option>
        <option>A</option>
        <option value="2">B</option>
        <option value="3">C</option>
      </select>
      <span>Selected: {{ selected }}</span>
    </div>
  </div>
</template>

<script>
  export default {
    name:"v-model",
    data(){
      return {
        title: &#39;v-model学习&#39;,
        selected: []
      }
    }
  }
</script>

<style scoped>
  .p1{
    text-align: left;
  }
  .spancss1{
    float: left;
  }
</style>

3. v-model modifier

3.1 .lazy

By default, v-model synchronizes the value of the input box with the data after each input event is triggered. (Except when input method combines text). You can add the lazy modifier to switch to using onchange event is synchronized. When data is entered in the input box, the data will not change immediately. When the cursor leaves the input box, the data will be changed synchronously. The sample code is as follows:

<template>
  <div>
    <p class="p1">{{title}}</p>
    <div class="spancss1">
      <!-- 在“change”时而非“input”时更新 -->
      <input type="text" id="names" v-model.lazy="msg" ><br/>
      <label>输入值：</label>{{msg}}
    </div>
  </div>
</template>

<script>
  export default {
    name:"v-model",
    data(){
      return {
        title: &#39;v-model学习&#39;,
        msg: &#39;&#39;
      }
    }
  }
</script>

<style scoped>
  .p1{
    text-align: left;
  }
  .spancss1{
    float: left;
  }
</style>

3.2 .number

If you want to automatically convert the user’s input value to a numerical type, define type as number type and add the number modifier to v-model , when the user enters numerical type data, v-model.number will automatically convert the input data into a numerical type. Note that if the user enters the special letter e, the number attribute cannot be recognized. A simple code example is as follows:

<template>
  <div>
    <p class="p1">{{title}}</p>
    <div class="spancss1">
      <!-- 在“change”时而非“input”时更新 -->
      <input type="number" id="names" v-model.number="msg" ><br/>
      <label>输入值：</label>{{msg}}
    </div>
  </div>
</template>

<script>
  export default {
    name:"v-model",
    data(){
      return {
        title: &#39;v-model学习&#39;,
        msg: &#39;&#39;
      }
    }
  }
</script>

<style scoped>
  .p1{
    text-align: left;
  }
  .spancss1{
    float: left;
  }
</style>

3.3 .trim

If you want to automatically filter the leading and trailing blank characters entered by the user, you can add the trim modifier to v-model, in Add a few more spaces at the beginning of the input box. When the cursor leaves, the trim attribute will automatically filter the ending spaces. A simple code example is as follows:

<template>
  <div>
    <p class="p1">{{title}}</p>
    <div class="spancss1">
      <label>无trim属性</label>
      <input type="text" id="names" v-model="msg1" ><br/>
      <label>输入值：</label>{{msg1}}<br/>
      <label>有trim属性</label>
      <input type="text" id="names2" v-model.trim="msg2" ><br/>
      <label>输入值：</label>{{msg2}}
    </div>
  </div>
</template>

<script>
  export default {
    name:"v-model",
    data(){
      return {
        title: &#39;v-model学习&#39;,
        msg1: &#39;&#39;,
        msg2: &#39;&#39;
      }
    }
  }
</script>

<style scoped>
  .p1{
    text-align: left;
  }
  .spancss1{
    float: left;
  }
</style>

4. Used in components v-model

4.1 自定义组件v-model

一个组件上的 v-model 默认会利用名为 value 的 prop 和名为 input 的事件，但是像输入框、单选框、复选框等类型的输入控件可能会将 value 特性用于不同的目的。本文以自定义输入框和onchange事件为例，在输入框输入值，当光标离开以后输入值会输出绑定到置顶位置：

1. 在index中声明组件（在index声明的组件为全局组件，全局可用）：

Vue.component('base-text', {
  model: {
    prop: 'value',
    event: 'change'
  },
  props: {
    checked: Boolean
  },
  template: `<input>`
});
=

2. 在要使用该组件的插件中声明：

<template>
  <div>
    <p class="p1">{{title}}</p>
    <div class="spancss1">
     <base-text v-model="msg"></base-text><br/>
      <label>你输入了:</label>{{msg}}
    </div>
  </div>
</template>

<script>
  export default {
    name:"v-model",
    data(){
      return {
        title: &#39;v-model学习&#39;,
        msg: &#39;&#39;
      }
    }
  }
</script>

<style scoped>
  .p1{
    text-align: left;
  }
  .spancss1{
    float: left;
  }
</style>

3. 结果示例如下：

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