Let's talk about the modifiers in the Vue command, a summary of common event modifiers

This article will talk about the modifiers in vue instructions, compare the instruction modifiers in vue and the event objects in dom events, and introduce the commonly used event modifiers. I hope it will be useful to everyone. Helps!

Compare the instruction modifiers in vue and the event object in the dom event

Before talking about the modifiers in vue , we use the common methods/attributes of event objects used in DOM operations. What are the attributes of event? The attributes of the events I have used are as follows:

1. Prevent default event jumps (such as the jump of the href of the a tag and the submission of the form) (Learning video sharing: vue video tutorial )

event.preventDefault()

2. Prevent bubbling events (for example, the parent element binds the event, and the child element also binds the event. If the bubbling is not cancelled, clicking the child
element will also trigger the parent Element's event

event.stopPropagation()

3. Prevent subsequent events from being triggered. If written in A, the subsequently registered event B will not be triggered (for example, a button binds two events,
Pass [Priority Level] registered A and B, B does not run when running A)

event.stopImmediatePropagation()

4. The element that binds the event, such as ul binding event, and then click li, then currentTarget The return is ul

event.currentTarget

5. The element where the event occurred, such as ul binding event, and then clicking li, the target return is the clicked li.

event.target

The above are some attributes/methods that operate in the DOM tree, but using the Vue framework does not require these DOM operations. The methods in Vue have better and more concise syntax modifiers to implement various functions.

Event Modifier

In the event handler, there are always some functions that need to be modified, such as preventing certain default event jumps and submitting events without reloading the page, etc. Etc. In order to solve this problem, vuejs provides some event modifiers for v-on. Modifiers are represented by instruction suffix names starting with a dot

What are the commonly used event modifiers? ?

• .stop
• .prevent
• .capture
• .once

.stop

The printed result without adding .stop

##The printed result with added .stop

Source code:

  <template >
  <div @click="fnFather">
    <!-- 阻止事件冒泡 -->
    <button @click.stop="fn">阻止事件冒泡</button>
  </div>
</template>
<script>
export default {
  methods: {
    fn() {
      console.log("按钮点击了");
    },
    fnFather() {
      console.log("父元素 点击了");
    },
  },
};
</script>
<style>
</style>

Come to conclusion

When you click on a child element, the parent element will also be triggered, which is event bubbling.

Use .stop to prevent event bubbling, which means to prevent the event of the child element from propagating to the parent element.

.prevent

Not added .prevent<span style="font-size: 16px;"></span>Effect of attributes

##Added.prevent<span style="font-size: 16px;"></span>Effect of attributes

Source code

<template >
  <div>
    <!-- .prevent 阻止默认事件跳转 -->
    <a href="http://taobao.com" @click.prevent="eve">阻止跳转到淘宝</a>
  </div>
</template>
<script>
export default {
  methods: {
    eve() {
      console.log("按钮点击了");
    },
  },
};
</script>

Conclusion

The href attribute in the a tag will jump to the page. When you use the a tag to do some functions and do not need the default jump, you can use .prevent to prevent the default event jump. In fact, there are also form submission events that also use .prevent to prevent the default event from jumping

.capture

.capture

Its meaning is that although event capture is not commonly used, it is still important to understand =The following is a box with a structure of four divs

<template >
  <div @click="hand(&#39;最外层&#39;)">
    <div class="grandfather" @click="hand(&#39;抓到爷爷了&#39;)">
      <div class="father" @click="hand(&#39;抓到爸爸了&#39;)">
        <div class="son" @click="hand(&#39;抓到儿子了&#39;)"></div>
      </div>
    </div>
  </div>
</template>

There is no setting

.capture

It The order is to execute events from the inside out. This is a bubbling event.

Source code

<template >
  <div @click="hand(&#39;最外层&#39;)">
    <div class="grandfather" @click="hand(&#39;抓到爷爷了&#39;)">
      <div class="father" @click="hand(&#39;抓到爸爸了&#39;)">
        <div class="son" @click="hand(&#39;抓到儿子了&#39;)"></div>
      </div>
    </div>
  </div>
</template>
<script>
export default {
  methods: {
    hand(val) {
      console.log(val);
    },
  },
};
</script>

As shown in the figure

After setting

.capture

, it will be executed from the outside in. You can give a single setting or multiple settings

Source code

<template >
  <div @click.capture="hand(&#39;最外层&#39;)">
    <div class="grandfather" @click.capture="hand(&#39;抓到爷爷了&#39;)">
      <div class="father" @click.capture="hand(&#39;抓到爸爸了&#39;)">
        <div class="son" @click.capture="hand(&#39;抓到儿子了&#39;)"></div>
      </div>
    </div>
  </div>
</template>
<script>
export default {
  methods: {
    hand(val) {
      console.log(val);
    },
  },
};
</script>
<style>
div {
  margin: auto;
  display: flex;
  justify-content: center;
  align-items: center;
  width: 800px;
  height: 800px;
  background-color: green;
}
.grandfather {
  display: flex;
  justify-content: center;
  align-items: center;
  width: 500px;
  height: 500px;
  background-color: #ccc;
}
.father {
  display: flex;
  justify-content: center;
  align-items: center;
  width: 300px;
  height: 300px;
  background-color: red;
}
.son {
  width: 100px;
  height: 100px;

  background-color: skyblue;
}
</style>

As shown in the picture:

得出结论

冒泡是从里往外冒，捕获是从外往里捕.capture 它是事件捕获 当它存在时，会先从外到里的捕获，剩下的从里到外的冒泡。

.once

.once 含义是点击事件将只会触发一次 没有设置 .once 就是普通的函数正常执行

<template >
  <button @click="hand">函数只会执行一次</button>
</template>
<script>
export default {
  methods: {
    hand() {
      console.log("函数只会执行一次,再次点击不会执行");
    },
  },
};
</script>

设置了 .once 就只能执行一次

<template >
  <button @click.once="hand">函数只会执行一次</button>
</template>
<script>
export default {
  methods: {
    hand() {
      console.log("函数只会执行一次,再次点击不会执行");
    },
  },
};
</script>

得出结论

.once  就只能执行一次，再次点击就不会执行了

（学习视频分享：web前端开发、编程基础视频）

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