v-model数据双向绑定

a)  作用：数据双向绑定

b)  注意：绑定的是表单控件

c)  示例：计算器

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
</head>

<body>
    <div id='app'>
        <input type="text" v-model:value="num1">
        <select name="" id="" v-model:value="value">
            <option value="+">+</option>
            <option value="-">-</option>
            <option value="*">*</option>
            <option value="/">/</option>
        </select>
        <input type="text" v-model:value="num2">
        <button @click="getSum">=</button>
        <input type="text" v-model:value="sum">
    </div>
</body>
<script>
    let vue = new Vue({
        el: '#app',
        data: {
            value: "+",
            num1: "",
            num2: "",
            sum: "",
        },
        methods: {
            getSum() {
                // 1、eval()计算字符串，慎用
                // this.sum = eval(`${Number(this.num1)} ${this.value} ${Number(this.num2)}`)


                // 2、if判断
                // if (this.value == "+") {
                //     this.sum = Number(this.num1) + Number(this.num2)
                // } else if (this.value == "-") {
                //     this.sum = Number(this.num1) - Number(this.num2)
                // } else if (this.value == "*") {
                //     this.sum = Number(this.num1) * Number(this.num2)
                // } else {
                //     this.sum = Number(this.num1) / Number(this.num2)
                // }

                // 3、switch case
                switch (this.value) {
                    case "+":
                        this.sum = Number(this.num1) + Number(this.num2);
                        break;//结束本次判断，程序不往下执行
                    case "-":
                        this.sum = Number(this.num1) - Number(this.num2);
                        break;
                    case "*":
                        this.sum = Number(this.num1) * Number(this.num2);
                        break;
                    case "/":
                        this.sum = Number(this.num1) / Number(this.num2);
                        break;
                }
             
            }
        }
    })
</script>

</html>

 

posted @ 2021-09-13 20:31  从入门到入土  阅读(55)  评论(0)    收藏  举报