22.盘点购物车 

<style>
        * {
            margin: 0;
            padding: 0;
        }
        
        #app {
            width: 800px;
            height: 500px;
            margin: 50px auto;
            border: 1px solid #000;
            text-align: center;
        }
        
        nav {
            font-weight: 700;
            font-size: 20px;
            margin: 20px 0;
        }
        
        table {
            /* width: 600px;
            height: 300px; */
            border: 2px solid rgb(231, 206, 206);
            margin: 0 auto;
            border-collapse: collapse;
        }
        
        table tr {
            height: 30px;
            width: 600px;
        }
        
        table th,
        td {
            border: 2px solid rgb(231, 206, 206);
            padding: 10px;
        }
        
        p {
            margin: 10px 0 0 100px;
            text-align: left;
        }
        
        button {
            padding: 0 5px;
        }
        
        .show {
            text-align: center;
            margin: 50px auto;
        }
    </style>
<body>
    <div id="app">
        <div v-if="trs.length">
            <nav>图书购物车</nav>
            <table>
                <tr>
                    <th v-for="i in headers"> {{ i }} </th>
                </tr>
                <tr v-for="(item,index) in trs">
                    <td> {{ item.id }} </td>
                    <td> {{ item.name }} </td>
                    <td> {{ item.dates }} </td>
                    <!-- <td> {{ "￥"+item.price.toFixed(2) }} </td> -->
                    <!-- 可以直接在{{}} 里面用JS方法保留两个小数 .toFixed()  不过因为总价格也是这个格式 最好用过滤器如下-->
                    <td> {{ item.price | showPrice }} </td>
                    <!-- 过滤器在 moustache语法中的写法  | 过滤器名字 -->
                    <td> <button @click="decrement(index)"> - </button> {{ item.num }}
                        <button @click="increment(index)"> + </button> </td>
                    <td> <button @click="remove(index)">{{ item.operation }}</button> </td>
                </tr>
            </table>
            <p>总价：{{ totalPrice | showPrice }} </p>
        </div>
        <div class="show" v-else>
            <h1>购物车空空如也啦</h1>
        </div>
    </div>
    <script src='https://cdn.jsdelivr.net/npm/vue@2.6.12/dist/vue.js'></script>
    <script>
        const app = new Vue({
            el: '#app',
            data: {

                headers: [" ", "书籍名称", "出版日期", "价格", "购买数量", "操作"],
                trs: [{
                    id: 1,
                    name: "《算法导论》",
                    dates: "2006-9",
                    price: 85,
                    num: 1,
                    operation: "移除"
                }, {
                    id: 2,
                    name: "《UNIX编程艺术》",
                    dates: "2006-9",
                    price: 59,
                    num: 1,
                    operation: "移除"
                }, {
                    id: 3,
                    name: "《编程珠玑》",
                    dates: "2006-9",
                    price: 45,
                    num: 1,
                    operation: "移除"
                }, {
                    id: 4,
                    name: "《代码大全》",
                    dates: "2006-9",
                    price: 125,
                    num: 1,
                    operation: "移除"
                }]
            },
            methods: {
                decrement(index) {
                    if (this.trs[index].num > 1) {
                        this.trs[index].num--;
                        // let newnum = this.trs[index].num;
                        // this.sum = newnum * this.trs[index].price;
                    }
                },
                increment(index) {
                    this.trs[index].num++;
                    // let newnum = this.trs[index].num;
                    // this.sum = newnum * this.trs[index].price;
                },
                remove(index) {
                    this.trs.splice(index, 1)
                }
            },
            filters: { // 过滤器
                showPrice(price) {
                    return "￥" + price.toFixed(2);
                }
            },
            computed: {
                totalPrice() {
                    // 1.用基础for循环来遍历
                    // let totalPrice = 0;
                    // for (let i = 0; i < this.trs.length; i++) {
                    //     totalPrice += this.trs[i].price * this.trs[i].num;
                    // }
                    // return totalPrice;

                    // 2.用 for in 遍历
                    // let totalPrice = 0;
                    // for (let i in this.trs) {
                    //     totalPrice += this.trs[i].price * this.trs[i].num;
                    // }
                    // return totalPrice;

                    // 3.用for...of  
                    // let totalPrice = 0; // 这里的i 就是当前数组元素的值
                    // for (let i of this.trs) {
                    //     totalPrice += i.price * i.num;
                    // };
                    // return totalPrice;

                    // 用reduce做
                    let totalPrice = 0;
                    return this.trs.reduce(function(preValue, tr) {
                        return preValue += tr.price * tr.num;
                    }, 0)
                }
            }
        })
    </script>
</body>

 

posted @ 2020-12-29 11:51  闭上耳朵  阅读(94)  评论(0)    收藏  举报