GuLi商城-前端基础Vue指令-单向绑定双向绑定

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