计数器

计数器实例：子组件从父组件获取counter数据，子组件有两个button按钮，通过点击事件$emit()向父级传递事件，在父级的emthods写方法，来改变counter值

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<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<!-- 子组件有+-按钮，父组件有counter数据 -->
	<div id="app">
		<child :childcounter="counter" @subnumber="fathersubnumber" @addnumber="fatheraddnumber"></child>
	</div>
	
	<template id="child">
		<div>
			<h2>当前计数:{{childcounter}}</h2>
			<button type="button" @click="childsubnumber">-</button>
			<button type="button" @click="childaddnumber">+</button>
		</div>
	</template>
	<script src="js/vue.js" type="text/javascript" charset="utf-8"></script>
	<script type="text/javascript">
		const child = {
			template:'#child',
			data(){
				return{
					message:'hello child'
					}
			},
			methods:{
				childsubnumber(){
					this.$emit('subnumber');
				},
				childaddnumber(){
					this.$emit('addnumber');
				}
			},
			props:{
				childcounter:{
					type:Number,
					default:0,
					required:true,
					}
			}
		}
		
		const app = new Vue({
			el:'#app',
			data:{
				message:'你好啊',
				counter:0
			},
			methods:{
				fathersubnumber(){
					this.counter--;
				},
				fatheraddnumber(){
					this.counter++;
				}
			},
			components:{
				child
			}
		})
	</script>
	</body>
</html>