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