Vue中的watch和computedVue中的watch和computed watch computed 计算属性se

watch

       <div id="app">
		<input type="text" v-model = 'msg'>
		<h3>{{msg}}</h3>
		<button @click = 'stus[0].name = "rose"'>改变</button>
		<h4>{{stus[0].name}}</h4>

	</div>
	<script type="text/javascript" src="vue.min.js"></script>
	<script type="text/javascript">
		
		// 总结一句话： watch 监听的是单个属性
		// 基本的数据类型 简单监视
		// 复杂的数据类型 深度监视
		new Vue({
			el:'#app',
			data(){
				return {
					msg:'',
					stus:[{name:'jack'}],
					num:0
				}
			},
			watch:{
				msg:function(newV,oldV){
					console.log(newV,oldV);

					if (newV === 'tusir') {

						console.log('tusir来了');
					}
				},
				// 监听复杂数据类型  object  array  深度监视
				stus:{
					deep:true,//深度监视
					handler:function(newV,oldV){
						console.log(newV[0].name);
					}
				}
			}
		});
	</script>

computed

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title></title>
	<style type="text/css">
		*{
			padding: 0;
			margin: 0;
		}
		ul{
			list-style: none;
		}
		ul li{
			margin: 20px 20px;
			padding: 10px 5px;
			border-radius: 3px;
		}
		ul li.active{
			background-color: #66FFFF;
		}
	</style>
</head>
<body>
	<div id="app">
		<audio :src = 'getCurrentSongSrc' autoplay controls></audio>
		<ul>
		    <li v-for = '(item,index) in musicData' @click = 'clickHandler(index)' :class = '{active:currentIndex == index}'>
		    	<h2>{{item.id}} - 歌名：{{item.name}}</h2>
		    	<p>歌手：{{item.songSrc}}</p>
		    </li>
		</ul>
	</div>
	<script type="text/javascript" src="vue.min.js"></script>
	<script type="text/javascript">
		var musicData = [

			{id:1,name:'于荣光 - 少林英雄',author:'于荣光',songSrc:'./static/于荣光 - 少林英雄.mp3'},

			{id:2,name:'Joel Adams - Please Dont Go',author:'Joel Adams',songSrc:'./static/Joel Adams - Please Dont Go.mp3'},

			{id:3,name:'MKJ - Time',author:'MKJ',songSrc:'./static/MKJ - Time.mp3'},

			{id:4,name:'Russ - Psycho (Pt. 2)',author:'Russ',songSrc:'./static/Russ - Psycho (Pt. 2).mp3'}

		];

		new Vue({
			el:'#app',
			data(){
				return {
					musicData:musicData,
					currentIndex:0
				}
			},
			computed:{
				// 计算属性默认只有getter
				// setter 也可以
				getCurrentSongSrc:function(){
					return this.musicData[this.currentIndex].songSrc

				}
			},
			methods:{
				clickHandler(index){
					// 1
					this.currentIndex = index;
				}
			}
		});


	</script>
	
</body>
</html>

计算属性setter

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title></title>
	<style type="text/css">
		*{
			padding: 0;
			margin: 0;
		}
		ul{
			list-style: none;
		}
		ul li{
			margin: 20px 20px;
			padding: 10px 5px;
			border-radius: 3px;
		}
		ul li.active{
			background-color: #66FFFF;
		}
	</style>
</head>
<body>
	<div id="app">
		<audio :src = 'getCurrentSongSrc' autoplay controls></audio>
		<ul>
		    <li v-for = '(item,index) in musicData' @click = 'clickHandler(index)' :class = '{active:currentIndex == index}'>
		    	<h2>{{item.id}} - 歌名：{{item.name}}</h2>
		    	<p>歌手：{{item.songSrc}}</p>
		    </li>
		</ul>
	</div>
	<script type="text/javascript" src="vue.min.js"></script>
	<script type="text/javascript">
		var musicData = [

			{id:1,name:'于荣光 - 少林英雄',author:'于荣光',songSrc:'./static/于荣光 - 少林英雄.mp3'},

			{id:2,name:'Joel Adams - Please Dont Go',author:'Joel Adams',songSrc:'./static/Joel Adams - Please Dont Go.mp3'},

			{id:3,name:'MKJ - Time',author:'MKJ',songSrc:'./static/MKJ - Time.mp3'},

			{id:4,name:'Russ - Psycho (Pt. 2)',author:'Russ',songSrc:'./static/Russ - Psycho (Pt. 2).mp3'}

		];

		new Vue({
			el:'#app',
			data(){
				return {
					musicData:musicData,
					currentIndex:0
				}
			},
			computed:{
				// 计算属性默认只有getter
				// setter 也可以
				// getCurrentSongSrc:function(){
				// 	return this.musicData[this.currentIndex].songSrc

				// }
				getCurrentSongSrc:{
					set:function(newV){
						console.log(newV);
						this.currentIndex   = newV
					},
					get:function(){
						return this.musicData[this.currentIndex].songSrc;
					}
				}

			},
			methods:{
				clickHandler(index){
					
					// 直接修改的数据属性
					// this.currentIndex = index;
					// 点语法    set方法和get方法
					// getter方法
					console.log(this.getCurrentSongSrc);
					this.getCurrentSongSrc = index;
				}
			}
		});


	</script>
	
</body>
</html>