vue购物车案例、v-model进阶、与后端交互

一购物车案例

- 结算

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>购物车结算</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.6.12/vue.min.js"></script>
    <style>
        table, td {
            border: 1px solid black;
            text-align: center;
        }
    </style>
</head>
<body>
<div id="box">
    <table>
        <tr>
            <td>商品名称</td>
            <td>价格</td>
            <td>数量</td>
            <td>选择</td>
        </tr>
        <tr v-for="item in dataList">
            <td>{{item.name}}</td>
            <td>{{item.price}}</td>
            <td>{{item.number}}</td>
            <td><input type="checkbox" :value="item" v-model="checkGroup"></td>
        </tr>
    </table>
    <br>已选商品：{{checkGroup}}
    <br>总价：{{getPrice()}}
</div>
</body>
<script>
    var vm = new Vue({
        el: '#box',
        data: {
            dataList: [
                {name: '今瓶没', price: 99, number: 2},
                {name: '西柚记', price: 59, number: 1},
                {name: '水壶转', price: 89, number: 5},
            ],
            checkGroup: [],
        },
        methods: {
            getPrice() {
                let sum_price = 0
                for (i in this.checkGroup) {    // 这里的 i 是索引
                    sum_price += this.checkGroup[i]['number'] * this.checkGroup[i]['price']
                }
                return sum_price
            }
        }
    })
</script>
</html>

- 全选/全不选

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>全选/全不选</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.6.12/vue.min.js"></script>
    <style>
        table, td {
            border: 1px solid black;
            text-align: center;
        }
    </style>
</head>
<body>
<div id="box">
    <table>
        <tr>
            <td>商品名称</td>
            <td>价格</td>
            <td>数量</td>
            <td>全选/全不选<input type="checkbox" v-model="allChecked" @change="checkAll"></td>
        </tr>
        <tr v-for="item in dataList">
            <td>{{item.name}}</td>
            <td>{{item.price}}</td>
            <td>{{item.number}}</td>
            <td><input type="checkbox" :value="item" v-model="checkGroup" @change="checkOne"></td>
        </tr>
    </table>
    <br>已选商品：{{checkGroup}}
    <br>总价：{{getPrice()}}
</div>
</body>
<script>
    var vm = new Vue({
        el: '#box',
        data: {
            dataList: [
                {name: '今瓶没', price: 99, number: 2},
                {name: '西柚记', price: 59, number: 1},
                {name: '水壶转', price: 89, number: 5},
            ],
            checkGroup: [],
            allChecked: false,
        },
        methods: {
            getPrice() {
                let sum_price = 0
                for (i in this.checkGroup) {    // 这里的 i 是索引
                    sum_price += this.checkGroup[i]['number'] * this.checkGroup[i]['price']
                }
                return sum_price
            },
            checkAll() {
                if (this.checkGroup.length > 0) {
                    this.checkGroup = []
                } else {
                    this.checkGroup = this.dataList
                }
            },
            checkOne() {
                // if (this.checkGroup.length === this.dataList.length) {
                //     this.allChecked = true
                // } else {
                //     this.allChecked = false
                // }
                this.allChecked = this.checkGroup.length === this.dataList.length;
            }
        }
    })
</script>
</html>

- 数量加减

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>控制加减</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.6.12/vue.min.js"></script>
    <link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.3/css/bootstrap.min.css" rel="stylesheet">
</head>
<body>
<div class="row">
    <div id="box" class="col-md-4 offset-md-1 text-center mt-5 ">
        <table class="table table-bordered">
            <thead>
            <tr>
                <th scope="col">商品名称</th>
                <th scope="col">单价</th>
                <th scope="col">数量</th>
                <th scope="col">全选/全不选 <input type="checkbox" v-model="allChecked" @change="checkAll"></th>
            </tr>
            </thead>
            <tbody>
            <tr v-for="item in dataList">
                <td>{{item.name}}</td>
                <td>{{item.price}}</td>
                <td>
                    <button class="btn link btn-sm" @click="reduceNum(item)">-</button>
                    {{item.number}}
                    <button class="btn link btn-sm" @click="item.number++">+</button>
                </td>
                <td><input type="checkbox" :value="item" v-model="checkGroup" @change="checkOne"></td>
            </tr>
            <tr class="text-left">
                <td colspan="4">总价：{{getPrice()}}
            </tr>
            </tbody>
        </table>
    </div>
</div>
</body>
<script>
    var vm = new Vue({
        el: '#box',
        data: {
            dataList: [
                {name: '今瓶没', price: 99, number: 1},
                {name: '西柚记', price: 59, number: 1},
                {name: '水壶转', price: 89, number: 1},
            ],
            checkGroup: [],
            allChecked: false,
        },
        methods: {
            getPrice() {
                let sum_price = 0
                for (i in this.checkGroup) {
                    sum_price += this.checkGroup[i]['number'] * this.checkGroup[i]['price']
                }
                return sum_price
            },
            checkAll() {
                if (this.checkGroup.length > 0) {
                    this.checkGroup = []
                } else {
                    this.checkGroup = this.dataList
                }
            },
            checkOne() {
                // if (this.checkGroup.length === this.dataList.length) {
                //     this.allChecked = true
                // } else {
                //     this.allChecked = false
                // }
                this.allChecked = this.checkGroup.length === this.dataList.length;
            },
            reduceNum(item) {
                if (item.number === 1) {
                    item.number = 1
                } else {
                    item.number--
                }
            }
        }
    })
</script>
</html>

二：v-model进阶

v-model 之 lazy、number、trim

lazy：等待input框的数据绑定时区焦点之后再变化
number：数字开头，只保留数字，后面的字母不保留；字母开头，都保留
trim：去除首位的空格

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>v-model 之 lazy、number、trim</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.6.12/vue.min.js"></script>
</head>
<body>
<div id="box">
    <input type="text" v-model="myText1" placeholder="normal"> {{myText1}}
    <br>
    <input type="text" v-model.lazy="myText2" placeholder="lazy"> {{myText2}}
    <br>
    <input type="text" v-model.number="myText3" placeholder="number"> {{myText3}}
    <br>
    <input type="text" v-model.trim="myText4" placeholder="trim"> {{myText4}}
</div>
</body>
<script>
    var vm = new Vue({
        el: '#box',
        data: {
            myText1: '',
            myText2: '',
            myText3: '',
            myText4: '',
        },
    })
</script>
</html>

三与后端交互 - ajax

版本1 - 出现了跨域问题

前端：index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Vue与后端交互 - 出现了跨域问题</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.6.12/vue.min.js"></script>
</head>
<body>
<div id="box">
    <button @click="handleClick">加载数据</button>
</div>
</body>
<script>
    let vm = new Vue({
        el: '#box',
        data: {},
        methods: {
            handleClick() {
                $.ajax({
                    url: 'http://127.0.0.1:5000/',    // 发送请求的url，本地的5000端口，是flask的默认端口
                    method: 'get',
                    success: (data) => {
                        console.log(data)
                    }
                })
            }
        }
    })
</script>
</html>

后端：main.py

from flask import Flask    # 这里用轻量级的Flask框架来测试

app = Flask(__name__)


@app.route('/')
def index():
    print('请求来了')
    return 'Hello World'


if __name__ == '__main__':
    app.run()

这里可以看出：前端向后端成功发送了请求，后端也成功响应了，但是前端却报错了

这是因为：跨域问题的存在，浏览器检测到前端和后端不是来自同一个域，所以认为这是不安全的，所以就拦截了该资源的传递

想要解决这个问题，就要实现：CORS，也就是 跨域资源共享

版本2 - 解决了跨域问题

前端：index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Vue与后端交互 - 解决了跨域问题</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.6.12/vue.min.js"></script>
</head>
<body>
<div id="box">
    <button @click="handleClick">加载数据</button>
    <p>加载的数据：{{myText}}</p>
</div>
</body>
<script>
    let vm = new Vue({
        el: '#box',
        data: {
            myText: ''
        },
        methods: {
            handleClick() {
                $.ajax({
                    url: 'http://127.0.0.1:5000/',
                    method: 'get',
                    success: (data) => {
                        console.log(data)
                        this.myText = data
                    }
                })
            }
        }
    })
</script>
</html>

后端：main.py

from flask import Flask, make_response

app = Flask(__name__)


@app.route('/')
def index():
    print('请求来了')
    res = make_response('Hello World')
    res.headers['Access-Control-Allow-Origin'] = '*'    # 访问控制允许的源 设置为全部
    return res


if __name__ == '__main__':
    app.run()

版本3 - 后端读取json文件传到前端

json文件：file.json

{
  "name": "Darker",
  "age": "18",
  "gender": "male"
}

前端：index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Vue与后端交互 - json</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.6.12/vue.min.js"></script>
</head>
<body>
<div id="box">
    <button @click="handleClick">加载数据</button>
    <p>加载的数据：{{myText}}</p>
</div>
</body>
<script>
    let vm = new Vue({
        el: '#box',
        data: {
            myText: ''
        },
        methods: {
            handleClick() {
                $.ajax({
                    url: 'http://127.0.0.1:5000/',
                    method: 'get',
                    success: (data) => {
                        console.log(data)
                        this.myText = data
                    }
                })
            }
        }
    })
</script>
</html>

后端：main.py

import json

from flask import Flask, jsonify

app = Flask(__name__)


@app.route('/')
def index():
    print('请求来了')
    with open('file.json', mode='rt', encoding='utf-8') as f:
        dic = json.load(f)
    res = jsonify(dic)
    res.headers['Access-Control-Allow-Origin'] = '*'
    return res


if __name__ == '__main__':
    app.run()

fetch

1.简介

① fetch介绍

提供了一个 JavaScript 接口，用于访问和操纵 HTTP 管道的一些具体部分，例如请求和响应

它还提供了一个全局 fetch() 方法，该方法提供了一种简单，合理的方式来跨网络异步获取资源

② fetch基本格式

fetch('http://example.com/movies.json')
  .then(function(response) {
    return response.json();
  })
  .then(function(myJson) {
    console.log(myJson);
  });

2.实例

json文件：file.json

{
  "name": "Darker",
  "age": "18",
  "gender": "male"
}

后端：main.py

import json

from flask import Flask, jsonify

app = Flask(__name__)


@app.route('/')
def index():
    print('请求来了')
    with open('file.json', mode='rt', encoding='utf-8') as f:
        dic = json.load(f)
    res = jsonify(dic)
    res.headers['Access-Control-Allow-Origin'] = '*'
    return res


if __name__ == '__main__':
    app.run()

前端：index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Vue与后端交互 - fetch</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.6.12/vue.min.js"></script>
</head>
<body>
<div id="box">
    <button @click="handleClick">加载数据</button>
    <p>加载的数据：</p>
    <ul>
        <li >姓名：{{name}}</li>
        <li >年龄：{{age}}</li>
        <li >性别：{{gender}}</li>
    </ul>
</div>
</body>
<script>
    let vm = new Vue({
        el: '#box',
        data: {
            name:'',
            age: '',
            gender: ''
        },
        methods: {
            handleClick() {
                fetch('http://127.0.0.1:5000/').then(response => {
                    return response.json()
                }).then(json => {
                    console.log('从后端获取的json数据', json)   // success 获取的数据
                    this.name = json.name
                    this.age = json.age
                    this.gender = json.gender
                }).catch(ex => {
                    console.log('出现了异常', ex)    // 抛出异常
                })
            }
        }
    })
</script>
</html>