Vue v-on 指令

实例

单击按钮时，使用 v-on 指令更改 <div> 元素的背景色。

<template>
  <h1>v-on Example</h1>
  <div v-bind:class="{ yelClass: bgColor }">
    <p>Click the button to change background color of this DIV box.</p>
    <button v-on:click="bgColor = !bgColor">Click</button>
    <p>bgColor property: "{{ bgColor }}"</p>
  </div>
</template>

定义与用法

v-on 指令被放置在一个元素上，以附加一个事件监听器。要使用 v-on 附加事件监听器，我们需要提供事件类型、任何修饰符以及在该事件发生时应该运行的方法或表达式。

如果 v-on 被放置在一个常规的 HTML 标记上，那么我们可以定义要监听的事件类型是常规事件，如 input, click 或者 mouseover。

如果 v-on 放置在自定义组件上，那么我们可以定义要侦听的事件类型就是从该组件发出的自定义事件。

v-on: 的简写为 @。

修饰符

更多实例

实例 1

使用 .capture 修饰符首先捕获父元素中的单击事件。

<template>
  <h1>v-on Example</h1>
  <p>When the '.capture' modifier is used on the parent DIV element, the event is captured first in the parent element when the child element is clicked.</p>
  <p>If the '.capture' modifier is removed from this code, the child element will capture the click event first. This is the default behavior, that the event bubbles up, first in child element, then to the parent.</p>
  <div v-on:click.capture="this.msg.push('parent')" id="parent">
    <p>This is the parent element.</p>
    <div v-on:click="this.msg.push('child')">
      <p>This is the child element. CLICK HERE!</p>
    </div>
  </div>
  <p>The order of when and where the event is captured.</p>
  <ol>
    <li v-for="x in msg">{{ x }}</li>
  </ol>
</template>
<script>
export default {
  data() {
    return {
      msg: []
    };
  }
}
</script>
<style scoped>
div {
  margin: 10px;
  padding: 10px;
  border: dashed black 1px;
}
#parent {
  width: 250px;
  background-color: lightpink;
}
#parent > div {
  cursor: pointer;
  background-color: lightgreen;
}
</style>

实例 2

使用 .stop 修饰符来防止事件进一步传播。

<template>
  <h1>v-on Example</h1>
  <p>The '.stop' modifier stops the click event from propagating any further.</p>
  <p>If the '.stop' modifier is removed from this code, the parent element will also capture the click event on the child element.</p>
  <div v-on:click="this.msg.push('parent')" id="parent">
    <p>This is the parent element.</p>
    <div v-on:click.stop="this.msg.push('child')">
      <p>This is the child element. CLICK HERE!</p>
    </div>
  </div>
  <p>The order of when and where the event is captured.</p>
  <ol>
    <li v-for="x in msg">{{ x }}</li>
  </ol>
</template>
<script>
export default {
  data() {
    return {
      msg: []
    };
  }
}
</script>
<style scoped>
div {
  margin: 10px;
  padding: 10px;
  border: dashed black 1px;
}
#parent {
  width: 250px;
  background-color: lightpink;
}
#parent > div {
  cursor: pointer;
  background-color: lightgreen;
}
</style>

实例 3

在滚动过程中使用 .passive 修饰符来增强性能。

<template>
  <h1>v-on Example</h1>
  <p>The '.passive' modifier sets the event handler as passive, and this can enhance performance.</p>
  <div v-on:scroll.passive="this.scrollTimes++" id="parent">
    <p>Scroll here.</p>
    <p>Bladi-bladi-bladi</p>
    <p>potato potato</p>
    <p>Scroll-scroll-scroll</p>
    <p>Scroll more...</p>
  </div>
  <p>Scroll happended {{ scrollTimes }} times.</p>
</template>
<script>
export default {
  data() {
    return {
      scrollTimes: 0
    };
  }
}
</script>
<style scoped>
div {
  margin: 10px;
  padding: 10px;
  border: dashed black 1px;
  width: 200px;
  height: 50px;
  overflow: scroll;
  background-color: lightcoral;
}
</style>

实例 4

在滚动过程中使用 .once 修饰符来增强性能。

<template>
  <h1>v-on Example</h1>
  <p>The '.once' modifier prevents the event from happening more than once.</p>
  <button v-on:click.once="clickTimes++">Click</button>
  <p>Click event happened {{ clickTimes }} times.</p>
</template>
<script>
export default {
  data() {
    return {
      clickTimes: 0
    };
  }
}
</script>

实例 5

使用 .self 修饰符，使父元素仅对自身发生的单击事件作出反应。

<template>
  <h1>v-on Example</h1>
  <p>The '.self' modifier is set on the parent element. </p>
  <p>Click on the child element and see how the event propagates past the parent element because the parent click event only reacts to click on the element itself.</p>
  <div v-on:click="addMsg('grandParent')" id="grandParent">
    Grandparent element
    <div v-on:click.self="addMsg('parent')">
      Parent element.
      <div v-on:click="addMsg('child')">
        Child element. CLICK HERE!
      </div>
    </div>
  </div>
  <p>The order of when and where the event is captured.</p>
  <ol>
    <li v-for="x in msg">{{ x }}</li>
  </ol>
</template>
<script>
export default {
  data() {
    return {
      msg: []
    };
  },
  methods: {
    addMsg(txt) {
      this.msg.push(txt);
    }
  }
}
</script>
<style scoped>
div {
  margin: 10px;
  padding: 10px;
  border: dashed black 1px;
  cursor: pointer;
}
#grandParent {
  width: 250px;
  background-color: lightpink;
}
#grandParent > div {
  background-color: lightgreen;
}
#grandParent > div > div {
  background-color: lightskyblue;
}
</style>

实例 6

使用 .prevent 修饰符可以防止鼠标右键单击时出现默认的下拉列表。

<template>
  <h1>v-on Example</h1>
  <p>The '.prevent' modifier is set to prevent the drop down menu to appear when the user does a right mouse button click.</p>
  <div
    v-on:click.right.prevent="changeColor"
    v-bind:style="{ backgroundColor: 'hsl(' + bgColor + ',80%,80%)' }">
    <p>Press right mouse button here.</p>
  </div>
</template>
<script>
export default {
  data() {
    return {
      bgColor: 0
    }
  },
  methods: {
    changeColor() {
      this.bgColor += 50
    }
  }
}
</script>
<style scoped>
div {
  margin: 10px;
  padding: 10px;
  border: dashed black 1px;
  width: 200px;
}
</style>

实例 7

当用户在按住 shift 键的同时单击鼠标左键时，使用 .left.shift 修饰符来更改图片。

<template>
  <h1>v-on Example</h1>
  <p>Hold 'Shift' key and press left mouse button on the image:</p>
  <img v-on:click.left.shift="changeImg" v-bind:src="imgUrl">
</template>
<script>
export default {
  data() {
    return {
      imgFish: true,
      imgUrl: 'img_fish.svg'
    }
  },
  methods: {
    changeImg() {
      this.imgFish = !this.imgFish;
      if (this.imgFish) {
        this.imgUrl = 'img_fish.svg'
      }
      else {
        this.imgUrl = 'img_tiger.svg'
      }
    }
  }
}
</script>
<style scoped>
img {
  width: 200px;
}
</style>