Attribute analysis of simple event binding of v-on directive in Vue (with code)

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

Preface

The previous article introduced the use of the v-on instruction by taking the v-on instruction to bind the click event as an example. This article introduces some attributes of the v-on binding event. How to use.

v-on binding instruction attribute

.stop attribute

Prevents the click event from continuing to propagate upward (to put it simply, it does not Let the parent node and node events above the parent node trigger). If there is no stop attribute in this example, the parent node and grandpa node events will trigger, and the content will be output on the console. The sample code and sample results are as follows:

1 <template>
 2   <div>
 3     <p class="title1">{{title}}</p>
 4     <div class="div1">
 5       <div v-on:click="clickme0">
 6         {{ msg1}}
 7         <div v-on:click="clickme">
 8           {{msg2}}<br/>
 9           <span v-on:click="clickthis">{{msg3}}</span>
10         </div>
11       </div>
12     </div>
13   </div>
14 
15 </template>
16 
17 <script>
18   export default {
19     name: &#39;v-on&#39;,
20     data() {
21       return {
22         msg1: &#39;我是爷爷节点&#39;,
23         msg2: &#39;我是父节点&#39;,
24         msg3: &#39;测试click属性&#39;,
25         title: &#39;v-on指令学习&#39;
26       }
27     },
28     methods:{
29       clickme0(){
30         console.log("我是爷爷节点");
31       },
32       clickme(){
33         console.log("我是父节点");
34       },
35       clickthis(){
36         console.log("不打印父节点事件内容！")
37       }
38     }
39   }
40 </script>
41 
42 <style scoped>
43   .title1 {
44     text-align: left;
45   }
46   .div1{
47     float: left;
48   }
49 </style>

If you add the stop attribute, the parent node and grandpa node events will not be triggered, and the corresponding event content will not be output on the console. The sample code and sample results are as follows:

1 <template>
 2   <div>
 3     <p class="title1">{{title}}</p>
 4     <div class="div1">
 5       <div v-on:click="clickme0">
 6         {{ msg1}}
 7         <div v-on:click="clickme">
 8           {{msg2}}<br/>
 9           <span v-on:click.stop="clickthis">{{msg3}}</span>
10         </div>
11       </div>
12     </div>
13   </div>
14 
15 </template>
16 
17 <script>
18   export default {
19     name: &#39;v-on&#39;,
20     data() {
21       return {
22         msg1: &#39;我是爷爷节点&#39;,
23         msg2: &#39;我是父节点&#39;,
24         msg3: &#39;测试click属性&#39;,
25         title: &#39;v-on指令学习&#39;
26       }
27     },
28     methods:{
29       clickme0(){
30         console.log("我是爷爷节点");
31       },
32       clickme(){
33         console.log("我是父节点");
34       },
35       clickthis(){
36         console.log("不打印父节点事件内容！")
37       }
38     }
39   }
40 </script>
41 
42 <style scoped>
43   .title1 {
44     text-align: left;
45   }
46   .div1{
47     float: left;
48   }
49 </style>

.prevent attribute

This method will notify the web browser not to perform the default action associated with the event (if such an action exists). Note that if the Event If the object's cancelable property is fasle, then there is no default action, or the default action cannot be prevented. In either case, calling this property has no effect.

A simple example is as follows, in the page from form if the type attribute is "submit"

If prevent is not specified, the click event automatically triggers the from form The action jumps to the specified website. The sample code and example results are as follows:

<template>
     <div>
      <p class="title1">{{title}}</p>
       <div class="div1">
         <form action="http://www.baidu.com" v-on:submit="clickme">
          <button type="submit">{{msg}}</button>
         </form>
         <!--<a href="http://www.baidu.com"   v-on:click.prevent="banclickme">点我去百度</a>-->
       </div>
     </div>
 </template>

<script>
    export default {
         name: &#39;v-on&#39;,
         data() {
           return {
               title: &#39;v-on指令学习&#39;,
             msg: &#39;form表单默认点击打开百度&#39;
           }
         },
       methods:{
           clickme(){
               console.log("页面重新加载了");
             }
         // banclickme(){
         //     console.log("去不了百度吧")
         // }
         }
     }
   </script>

 <style scoped>
    .title1 {
         text-align: left;
       }
  .div1{
              float: left;
            }
</style>

If prevent is specified, the click event will not trigger the from form action to jump to the specified website. Example The code and example results are as follows:

<template>
     <div>
      <p class="title1">{{title}}</p>
       <div class="div1">
         <form action="http://www.baidu.com" v-on:submit.prevent="clickme">
          <button type="submit">{{msg}}</button>
         </form>
         <!--<a href="http://www.baidu.com"   v-on:click.prevent="banclickme">点我去百度</a>-->
       </div>
     </div>
 </template>

<script>
    export default {
         name: &#39;v-on&#39;,
         data() {
           return {
               title: &#39;v-on指令学习&#39;,
             msg: &#39;form表单默认点击打开百度&#39;
           }
         },
       methods:{
           clickme(){
               console.log("去不了百度吧");
             }
         // banclickme(){
         //     console.log("去不了百度吧")
         // }
         }
     }
   </script>

 <style scoped>
    .title1 {
         text-align: left;
       }
  .div1{
              float: left;
            }
</style>

##.capture property

Use the event capture mode when adding an event listener, that is, the event triggered by the element itself is first here Processed everywhere, and then handed over to internal elements for processing. When the bottom element

is clicked to trigger an event, the element with the listener is first searched for, and the element with the modifier is triggered first according to the node priority, and then the event is triggered. The own event, and finally the event bubbles up.

In this example, the printing of the grandfather node is triggered first, then the printing of the parent node is triggered, then the printing of the own node is triggered, and finally the printing of the great-grandfather node is triggered. The sample code and results are as follows:

<template>
  <div>
    <p class="title1">{{title}}</p>
    <div class="div1" v-on:click="click3">
      {{msg3}}<br/>
      <div class="div1" v-on:click.capture="click2">
        {{msg2}}<br/>
        <div class="div1" v-on:click.capture="click1">
          {{msg1}}<br/>
          <div v-on:click="click0">{{msg}}</div>
        </div>
      </div>
    </div>
  </div>
</template>

<script>
  export default {
    name: &#39;v-on&#39;,
    data() {
      return {
        title: &#39;v-on指令学习&#39;,
        msg: &#39;我是div内部子节点&#39;,
        msg1: &#39;我是div父节点&#39;,
        msg2: &#39;我是div爷爷节点&#39;,
        msg3: &#39;我是div曾祖父节点&#39;
      }
    },
    methods:{
      click0(){
        console.log("打印子节点");
      },
      click1(){
          console.log("打印父节点");
      },
      click2(){
        console.log("打印爷爷节点");
      },
      click3(){
        console.log("打印曾祖父节点");
      }
    }
  }
</script>

<style scoped>
  .title1 {
    text-align: left;
  }
  .div1{
    float: left;
  }
</style>

.self attribute

The handler function is only triggered when event.target is the current element itself, that is, the event is not triggered from internal elements. In layman's terms, only The event is triggered when the element itself is clicked. When the parent element is clicked to trigger the event or when the child element is clicked and the event bubbles up, the event of the element itself is not triggered.

This example does not print the event of the element itself when the parent node or child node is clicked. Example The code and example results are as follows:

<template>
  <div>
    <p class="title1">{{title}}</p>
    <div class="div1" v-on:click="click3">
      {{msg3}}<br/>
      <div class="div1" v-on:click.self="click2">
        {{msg2}}<br/>
        <div class="div1" v-on:click="click1">
          {{msg1}}<br/>
          <div v-on:click="click0">{{msg}}</div>
        </div>
      </div>
    </div>
  </div>
</template>

<script>
  export default {
    name: &#39;v-on&#39;,
    data() {
      return {
        title: &#39;v-on指令学习&#39;,
        msg: &#39;我是div内部子节点&#39;,
        msg1: &#39;我是div父节点&#39;,
        msg2: &#39;我是div爷爷节点&#39;,
        msg3: &#39;我是div曾祖父节点&#39;
      }
    },
    methods:{
      click0(){
        console.log("打印子节点");
      },
      click1(){
          console.log("打印父节点");
      },
      click2(){
        console.log("打印爷爷节点");
      },
      click3(){
        console.log("打印曾祖父节点");
      }
    }
  }
</script>

<style scoped>
  .title1 {
    text-align: left;
  }
  .div1{
    float: left;
  }
</style>

.once attribute

The click event will only be triggered once. In layman's terms, the element's own event can only be used once. , the event will not be triggered when the element is clicked for the second time, but it will not prevent the event from bubbling.

In this example, the child nodes and parent nodes are printed when the element is clicked for the first time, and the child nodes are not printed when the element is clicked for the second time, but are still printed. Parent node and above nodes, the sample code and strength results are as follows:

<template>
  <div>
    <p class="title1">{{title}}</p>
    <div class="div1" v-on:click="click3">
      {{msg3}}<br/>
      <div class="div1" v-on:click="click2">
        {{msg2}}<br/>
        <div class="div1" v-on:click="click1">
          {{msg1}}<br/>
          <div v-on:click.once="click0">{{msg}}</div>
        </div>
      </div>
    </div>
  </div>
</template>

<script>
  export default {
    name: &#39;v-on&#39;,
    data() {
      return {
        title: &#39;v-on指令学习&#39;,
        msg: &#39;我是div内部子节点&#39;,
        msg1: &#39;我是div父节点&#39;,
        msg2: &#39;我是div爷爷节点&#39;,
        msg3: &#39;我是div曾祖父节点&#39;
      }
    },
    methods:{
      click0(){
        console.log("打印子节点");
      },
      click1(){
          console.log("打印父节点");
      },
      click2(){
        console.log("打印爷爷节点");
      },
      click3(){
        console.log("打印曾祖父节点");
      }
    }
  }
</script>

<style scoped>
  .title1 {
    text-align: left;
  }
  .div1{
    float: left;
  }
</style>

.passive attribute

Default behavior of scrolling events ( That is, the scrolling behavior) will be triggered immediately without waiting for onScroll to complete, which includes the case of event.preventDefault()

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