v-show指令的作用是：根据真假切换元素的显示状态
原理是修改元素的display，实现显示隐藏
指令后面的内容，最终都会解析为布尔值
值为 true 显示，值为 false 元素隐藏
数据改变之后，对应元素的显示状态会同步更新
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>v-show指令</title>
</head>
<body>
<div id="app">
<input type="button" value="切换显示状态" @click="changeIsshow" />
<input type="button" value="累加年龄" @click="addAge" />
<img v-show="age>18" src="https://p3-juejin.byteimg.com/tos-cn-i-k3u1fbpfcp/f4c541c1221b432ba424cce46b485698~tplv-k3u1fbpfcp-zoom-1.image" alt="" />
<img v-show="isshow" src="https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1607609582851&di=721a9536fa79613a4ade85d4f6c061dd&imgtype=0&src=http%3A%2F%2Fattach.bbs.miui.com%2Fforum%2F201408%2F07%2F213601f2xz7usscm2z1mjh.jpg" alt=""/>
</div>
<!-- 开发环境版本，包含了有帮助的命令行警告 -->
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<script>
var app = new Vue({
el:"#app",
data:{
isshow:false,
age:17
},
methods:{
changeIsshow:function(){
this.isshow = !this.isshow;
},
addAge:function(){
this.age++;
}
}
})
</script>
</body>
</html>
