vue.js event binding

1. Add an event listener v-on

(1) using v-on instruction can add event listeners, syntax:
v-on: eventName = "the Fn" can be abbreviated to @: eventName = "the Fn"
(2) parameters: $ event is the element event of the current trigger, even if does not pass $ event, you can also use the event this parameter in the callback function

Basic use:

<div id="app">
    <button v-on:click="test">点我</button>
    <button v-on:click="test2('hello vue')">点我2</button>
    <button v-on:click="test3($event)">点我3</button>
    <button v-on:click="test4">点我4</button>
</div>

methods: {
    test() {
        console.log('hi');
    },
    test2(content) {
        console.log(content);
    },
    test3(event) {
        console.log(event.target);
    },
    test4(){
       //即使不传$event,在回调函数中也可以使用event这个参数
       console.log(event.target.innerText);
    }
}

Other events:

<body>
    <div id="app">
        <!-- 点击事件 -->
        <button @click="testClick">点我</button>
        <!-- input事件 -->
        <input type="text" @input="testInput">
        <!-- change事件 -->
        <select @change="testChange">
            <option value="020">广州</option>
            <option value="021">上海</option>
        </select>
    </div>
</body>
<script>
    new Vue({
        el:"#app",
        data:{},
        methods:{
            testClick(){
                console.log('Click')
            },
            testInput(){
                console.log('Input')
            },
            testChange(){
                console.log('Change')
            }
        }
    })
</script>

2. Event Modifier

Event modifier used to control the bubbling of events and default behavior, there are two:
.stop: to prevent the event from bubbling
.prevent: to prevent the default event

Basic use:

<!-- 阻止事件冒泡 -->
<div id="big" @click="test">
    <div id="small" @click.stop="test2"></div>
</div>
<!-- 阻止默认事件，点击a链接不会发生跳转，只会执行test方法的代码 -->
<a href="https://www.baidu.com/" @click.prevent="test">百度一下</a>

3. modifier keys

Key modifiers used to monitor whether a key is pressed

Use @keyup keyboard commands you can add events to the elements, such as:

<!-- 任何按键按下都会触发回调函数 -->
<textarea @keyup="testKeyup" cols="30" rows="10"></textarea>

If we want to press a specific key callback is triggered only if you add a modifier key or key code, for example:
Syntax: @keyup key modifier = callback function.
Syntax: @keyup key code = callback function.

<!-- 只有回车键按下的时候才会触发回调函数 -->
<!-- 下面的两种写法效果是一致的 -->

<!--使用按键码，回车键的keyCode是13 -->
<textarea @keyup.13="testKeyup" cols="30" rows="10"></textarea>
<!--使用按键修饰符，因为回车键比较常用，所以vue为他设置了名称，可以直接使用enter来代替。 -->
<textarea @keyup.enter="testKeyup" cols="30" rows="10"></textarea>

methods: {
    testKeyup() {
        console.log('回车键被按下了');
    }
}

Vue provides the vast majority of commonly used modifier keys:

.enter
.tab
.delete (capture "Delete" and "backspace" key)
.esc
.space
.up
.down
.left
.right

Remaining keys with key code

<!--q的keyCode是81，当按下q键时会触发test方法 -->
<input type="text" value="hello" @keyup.81="test">

You can custom key Vue.config.keyCodes = modified by the global key code from the key definition of modifiers, for example:

//q的keyCode是81
<input type="text" value="hello" @keyup.q="test">

Vue.config.keyCodes.q=81