什么是指令?
指令 (Directives) 是带有 `v-` 前缀的特殊特性。
指令特性的预期值是:单个 JavaScript 表达式。
指令的职责是,当表达式的值改变时,将其产生的连带影响,响应式地作用于DOM
例如我们在入门案例中的 v-on,代表绑定事件
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<div id="app">
{{msg}} {{1+1}} {{hello()}}<br/>
<span v-html="msg"></span>
<br/>
<span v-text="msg"></span>
</div>
<script src="../node_modules/vue/dist/vue.js"></script>
<script>
new Vue({
el:"#app",
data:{
msg:"<h1>Hello</h1>",
link:"http://www.baidu.com"
},
methods:{
hello(){
return "World"
}
}
})
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<!-- 给html标签的属性绑定 -->
<div id="app">
<a v-bind:href="link">gogogo</a>
<!-- class,style {class名:加上?}-->
<span v-bind:class="{active:isActive,'text-danger':hasError}"
:style="{color: color1,fontSize: size}">你好</span>
</div>
<script src="../node_modules/vue/dist/vue.js"></script>
<script>
let vm = new Vue({
el:"#app",
data:{
link: "http://www.baidu.com",
isActive:true,
hasError:true,
color1:'red',
size:'36px'
}
})
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<!-- 表单项,自定义组件 -->
<div id="app">
精通的语言:
<input type="checkbox" v-model="language" value="Java"> java<br/>
<input type="checkbox" v-model="language" value="PHP"> PHP<br/>
<input type="checkbox" v-model="language" value="Python"> Python<br/>
选中了 {{language.join(",")}}
</div>
<script src="../node_modules/vue/dist/vue.js"></script>
<script>
let vm = new Vue({
el:"#app",
data:{
language: []
}
})
</script>
</body>
</html>
注意:页面上显示的是小写的java,操作的是value里面大写的Java
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