$listeners 在vue中的使用 --初学
事件回传之 $listeners
组件由下向上回传事件
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="Generator" content="EditPlus®">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<title>vue测试</title>
<script src="https://cdn.jsdelivr.net/npm/vue@2.5.22/dist/vue.js"></script>
<style>
</style>
</head>
<body>
<div id="app">
<base-input
v-model="username"
label="基础输入组件"
@click.native="handleBaseInputClick"
v-on:focus="handleBaseInputFocus"
placeholder="请输入您的名字"
class="username-input"/>
</div>
<script>
// 注册组件
// 因为base-input的外层是一个label元素，所以默认情况下使用v-on:focus是无效的，所以需要配合$listeners使用，该属性可以把事件的监听指向组件中某个特定的元素
// 注意：如果父级的事件添加了.native修饰符，在$listeners中不会体现出来的
Vue.component('base-input',{
inheritAttrs: false,
props: ['label','value'],
template: `
<label id="base-label">
{{label}}
<input v-bind:value="value" v-bind="$attrs" v-on="inputListeners"/>
</label>
`,
data: function() {
return {
}
},
computed: {
inputListeners () {
var vm = this
return Object.assign({},
this.$listeners,
{
input: function () {
vm.$emit('input', event.target.value)
},
focus: function (event) {
vm.$emit('focus', '哈哈哈，onfocus了')
}
}
)
}
},
mounted: function(){
console.log(`$attrs:`)
console.log(this.$attrs)
console.log(`$listeners:`)
console.log(this.$listeners) // 父级添加的所有属性都在这里
},
methods: {
}
})
var vm = new Vue({
el: '#app',
data: {
username: ''
},
created: function(){
},
beforeUpdate: function(){
},
computed: {
},
beforeUpdate: function () {
console.log(this.username)
},
methods: {
handleBaseInputFocus: function(ev){
console.log(ev)
},
handleBaseInputClick: function(ev){
console.log(ev.type)
}
}
})
</script>
</body>
</html>
-----------------------------------------------------------
实例二
<div id="app">
<child1
:p-child1="child1"
:p-child2="child2"
:p-child-attrs="1231"
v-on:test1="onTest1"
v-on:test2="onTest2">
</child1>
</div>
<script>
Vue.component("Child1", {
inheritAttrs: true,
props: ["pChild1"],
template: `
<div class="child-1">
<p>in child1:</p>
<p>props: {{pChild1}}</p>
<p>$attrs: {{this.$attrs}}</p>
<hr>
<child2 v-bind="$attrs" v-on="$listeners"></child2></div>`,
mounted: function() {
this.$emit("test1");
}
});
Vue.component("Child2", {
inheritAttrs: true,
props: ["pChild2"],
template: `
<div class="child-2">
<p>in child->child2:</p>
<p>props: {{pChild2}}</p>
<p>$attrs: {{this.$attrs}}</p>
<button @click="$emit('test2','按钮点击')">触发事件</button>
<hr> </div>`,
mounted: function() {
this.$emit("test2");
}
});
const app = new Vue({
el: "#app",
data: {
child1: "pChild1的值",
child2: "pChild2的值"
},
methods: {
onTest1() {
console.log("test1 running...");
},
onTest2(value) {
console.log("test2 running..." + value)