<!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>添加屬性</title>
    <!--引入vue.js-->
    <script src="node_modules/vue/dist/vue.js" ></script>
    <script>
        window.onload=function(){
            new Vue({
                el:'#app',// 2.0不允許掛載到html,body元素上
                data:{
                    info:{id:1,price:15,name:"套餐A"}
                },
                methods:{
                    add:function(){
                        // 給info對(duì)象添加msg屬性并賦值
                        this.info.msg="hello";
                    }
                }
            });
        }
    </script>
</head>
<body>
    <div id="app">
        {{info.msg}}
        <button @click="add">添加</button>
    </div>
</body>
</html>

先看看點(diǎn)擊按鈕之前的效果：

從截圖中可以看出這時(shí)info對(duì)象只有三個(gè)屬性，點(diǎn)擊“添加”按鈕刷新，然后在看看info對(duì)象的屬性，截圖如下：

可以看出這時(shí)info對(duì)象增加了msg屬性，但是界面上面沒有顯示出來(lái)msg屬性的值。即：

如果在實(shí)例創(chuàng)建之后添加新的屬性到實(shí)例上，不會(huì)觸發(fā)視圖更新。

這時(shí)就需要使用$set了。代碼示例如下：

<!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>添加屬性</title>
    <!--引入vue.js-->
    <script src="node_modules/vue/dist/vue.js" ></script>
    <script>
        window.onload=function(){
            new Vue({
                el:'#app',// 2.0不允許掛載到html,body元素上
                data:{
                    info:{id:1,price:15,name:"套餐A"}
                },
                methods:{
                    add:function(){
                        // 給info對(duì)象添加msg屬性并賦值
                        //this.info.msg="hello";
                        this.$set(this.info,"msg","hello");
                    }
                }
            });
        }
    </script>
</head>
<body>
    <div id="app">
        {{info.msg}}
        <button @click="add">添加</button>
    </div>
</body>
</html>

效果：

可以看出：使用了$set之后視圖會(huì)被更新。

注意：如果是修改對(duì)象里面已經(jīng)存在的屬性，則直接修改即可

代碼示例如下：

<!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>添加屬性</title>
    <!--引入vue.js-->
    <script src="node_modules/vue/dist/vue.js" ></script>
    <script>
        window.onload=function(){
            new Vue({
                el:'#app',// 2.0不允許掛載到html,body元素上
                data:{
                    info:{id:1,price:15,name:"套餐A"}
                },
                methods:{
                    add:function(){
                        // 給info對(duì)象添加msg屬性并賦值
                        //this.info.msg="hello";
                        this.$set(this.info,"msg","hello");
                    },
                    modify:function(){
                        this.info.name="套餐B";
                    }
                }
            });
        }
    </script>
</head>
<body>
    <div id="app">
        {{info.msg}}
        name值：{{info.name}}
        <button @click="add">添加</button>
        <button @click="modify">修改</button>
    </div>
</body>
</html>

效果：

二、$delete刪除對(duì)象屬性

可以使用$delete刪除對(duì)象里面的屬性，代碼示例如下：

<!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>添加屬性</title>
    <!--引入vue.js-->
    <script src="node_modules/vue/dist/vue.js" ></script>
    <script>
        window.onload=function(){
            new Vue({
                el:'#app',// 2.0不允許掛載到html,body元素上
                data:{
                    info:{id:1,price:15,name:"套餐A"}
                },
                methods:{
                    add:function(){
                        // 給info對(duì)象添加msg屬性并賦值
                        //this.info.msg="hello";
                        this.$set(this.info,"msg","hello");
                    },
                    modify:function(){
                        this.info.name="套餐B";
                    },
                    del:function(){
                        // 刪除info對(duì)象里面的price屬性
                        this.$delete(this.info,"price");
                    }
                }
            });
        }
    </script>
</head>
<body>
    <div id="app">
        {{info.msg}}
        name值：{{info.name}}
        <button @click="add">添加</button>
        <button @click="modify">修改</button>
        <button @click="del">刪除</button>
    </div>
</body>
</html>

效果：