vue购物车案例、v-model进阶、与后端交互-编程知识

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 = 0for (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 = 0for (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 = 0for (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_responseapp = 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 resif __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 jsonfrom flask import Flask, jsonifyapp = 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 resif __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 jsonfrom flask import Flask, jsonifyapp = 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 resif __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.namethis.age = json.agethis.gender = json.gender}).catch(ex => {console.log('出现了异常', ex)    // 抛出异常})}}})
</script>
</html>