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Vue生命周期与后端交互实现流程详解

作者:皮糖小王子

Vue的生命周期就是vue实例从创建到销毁的全过程,也就是new Vue()开始就是vue生命周期的开始。Vue实例有⼀个完整的⽣命周期,也就是从开始创建、初始化数据、编译模版、挂载Dom->渲染、更新->渲染、卸载等⼀系列过程,称这是Vue的⽣命周期

表单控制

1.input:checkbox(单选,多选),radio(单选)

2.代码展示

<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <title>Title</title>
   <script src="js/vue.js"></script>
</head>
<body>
<div id="app">
   <h1>表单控制</h1>
   <p>用户名:<input type="text" v-model="name"></p>
   <p>密码:<input type="text" v-model="password"></p>
   <p><input type="checkbox" v-model="isRemember">记住密码</p>
   <p>
       <input type="radio" v-model="gender" value="1">男
       <input type="radio" v-model="gender" value="2">女
       <input type="radio" v-model="gender" value="0">未知
   </p>
   <p>
       爱好:
       <input type="checkbox" value="篮球" v-model="hobby">篮球
       <input type="checkbox" value="足球" v-model="hobby">足球
       <input type="checkbox" value="乒乓球" v-model="hobby">乒乓球
       <input type="checkbox" value="排球" v-model="hobby">排球
   </p>
   {{hobby}}
</div>
</body>
<script>
   new Vue({
       el:'#app',
       data:{
           name:'',
           password:'',
           isRemember:false,   //checkbox单选,使用布尔类型
           gender:'',    //radio单选,使用字符串
           hobby:[]      //checkbox多选使用数组
       }
   })
</script>
</html>

购物车案例

1.python中只有基于迭代的循环可没有基于索引的循环

2.js,java,go基于迭代和索引的两种

3.js中for循环

代码展示:

   1 方式一:js的基于索引的循环
   for (var i = 0; i< goodList.length; i++) {
       console.log(goodList[i])
   }
   2 方式二:基于迭代的循环
   for (i in goodList){
       console.log(goodList[i])
   }
   3 方式三:of 循环,基于迭代的
     for (i of goodList){
       console.log(i)
   }
   4 方式四:数组的循环方法
   goodList.forEach(item => {
       console.log('---', item)
   })
   5 jquery:引入
   $.each(goodList, (i, v) => {
       console.log(v)
   })

4.基本购物车代码展示

<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <title>Title</title>
   <script src="./js/vue.js"></script>
   <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.0/jquery.js"></script>
   <link rel="stylesheet" >href="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css" rel="external nofollow"  rel="external nofollow" >
</head>
<body>
<div id="app">
   <div class="container-fluid">
       <h1 class="text-center">购物车</h1>
       <div class="row">
           <div class="col-md-6 col-md-offset-3">
               <table class="table table-bordered">
                   <thead>
                   <tr>
                       <th>商品id</th>
                       <th>商品名字</th>
                       <th>商品价格</th>
                       <th>商品数量</th>
                   </tr>
                   </thead>
                   <tbody>
                   <tr v-for="good in goodList">
                       <th>{{good.id}}</th>
                       <td>{{good.name}}</td>
                       <td>{{good.price}}</td>
                       <td>{{good.count}}</td>
                       <td><input type="checkbox" v-model="checkGroup" :value="good"></td>
                   </tr>
                   </tbody>
               </table>
               <hr>
               选中的商品是:{{checkGroup}}
               <br>
               总价格是:{{getPrice()}}
           </div>
       </div>
   </div>
</div>
</body>
<script>
   new Vue({
       el: '#app',
       data: {
           goodList: [
               {id: 1, name: '小汽车', price: 1200000, count: 1},
               {id: 2, name: '钢笔', price: 12, count: 34},
               {id: 3, name: '鸡蛋', price: 2, count: 4},
               {id: 4, name: '面包', price: 9, count: 10},
           ],
           checkGroup: []
       },
       methods: {
           getPrice() {
               // 取出checkGroup中得商品数量和商品价格相乘 做累加
               // js 中 for 循环
               var total = 0
               for (item of this.checkGroup) {
                   total += item.price * item.count
               }
               return total
           }
       }
   })
   var goodList = [
       {id: 1, name: '小汽车', price: 1200000, count: 1},
       {id: 2, name: '钢笔', price: 12, count: 34},
       {id: 3, name: '鸡蛋', price: 2, count: 4},
       {id: 4, name: '面包', price: 9, count: 10},
   ]
</script>
</html>

5.带加减的购物车代码展示

<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <title>Title</title>
   <script src="./js/vue.js"></script>
   <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css" rel="external nofollow"  rel="external nofollow" >
</head>
<body>
<div id="app">
   <div class="container-fluid">
       <h1 class="text-center">购物车</h1>
       <div class="row">
           <div class="col-md-6 col-md-offset-3">
               <table class="table table-bordered">
                   <thead>
                   <tr>
                       <th>商品id</th>
                       <th>商品名字</th>
                       <th>商品价格</th>
                       <th>商品数量</th>
                       <th><input type="checkbox" v-model="checkAll" @change="handleChange">全选/全不选</th>
                   </tr>
                   </thead>
                   <tbody>
                   <tr v-for="good in goodList">
                       <th>{{good.id}}</th>
                       <td>{{good.name}}</td>
                       <td>{{good.price}}</td>
                       <td><span class="btn link btn-sm" @click="handleDown(good)">-</span>{{good.count}}<span
                               class="btn link btn-sm" @click="good.count++">+</span>
                       </td>
                       <td><input type="checkbox" v-model="checkGroup" :value="good" @change="handleCheckOne"></td>
                   </tr>
                   </tbody>
               </table>
               <hr>
               选中的商品是:{{checkGroup}}
               <br>
               总价格是:{{getPrice()}}

           </div>
       </div>
   </div>
</div>
</body>
<script>
   new Vue({
       el: '#app',
       data: {
           goodList: [
               {id: 1, name: '小汽车', price: 1200000, count: 1},
               {id: 2, name: '钢笔', price: 12, count: 34},
               {id: 3, name: '鸡蛋', price: 2, count: 4},
               {id: 4, name: '面包', price: 9, count: 10},
           ],
           checkGroup: [],
           checkAll: false,
       },
       methods: {
           getPrice() {
               var total = 0
               for (item of this.checkGroup) {
                   total += item.price * item.count
               }
               return total
           },
           handleChange() {
               if (this.checkAll) {
                   this.checkGroup = this.goodList
               } else {
                   this.checkGroup = []
               }
           },
           handleCheckOne() {
               // 如果checkGroup的长度等于goodList的长度,说明全选了,checkAll就应该变为true,否则就是false
               // if (this.checkGroup.length == this.goodList.length) {
               //     this.checkAll = true
               // } else {
               //     this.checkAll = false
               // }
               // 变短
               this.checkAll = this.checkGroup.length == this.goodList.length
           },
           handleDown(good) {
               if (good.count > 1) {
                   good.count--
               } else {
                   alert('不能再少了,受不了了')
               }
           }
       }
   })
</script>
</html>

v-model进阶(了解)

1.v-model 之 lazy、number、trim

2.代码展示

<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <title>Title</title>
   <script src="./js/vue.js"></script>
</head>
<body>
<div id="app">
   <h1>v-model进阶</h1>
   <input type="text" v-model.lazy ="name1">----->{{name1}}
   <br>
   <input type="text" v-model.number ="name2">----->{{name2}}
   <br>
  <input type="text" v-model.trim ="name3">----->{{name3}}
</div>
</body>
<script>
   var vm = new Vue({
       el: '#app',
       data: {
           name1: '',
           name2:'',
           name3:'',
       },
   })
</script>
</html>

vue生命周期

1.var vm=new Vue实例()

四个过程:

2.八个钩子函数

4个过程对应八个函数,依次执行(到某个过程就会执行某个函数)

    beforeCreate    创建Vue实例之前调用,data,el都没有
   created            创建Vue实例成功后调用(可以在此处发送异步请求后端数据),data有了,el没有的
   beforeMount        渲染DOM之前调用 ,data有了,el没有
   mounted            渲染DOM之后调用
   beforeUpdate    重新渲染之前调用(数据更新等操作时,控制DOM重新渲染)
   updated            重新渲染完成之后调用
   beforeDestroy    销毁之前调用
   destroyed        销毁之后调用

钩子函数(hook),AOP的体现:面向切面编程----》装饰器实现aop;

3.学习生命周期需要掌握

4.小案例:

组件创建,开启定时器,不停的打印hello,在destroyed中对定时器进行销毁。 补充之js定时任务和延时任务: 延时任务:

setTimeout(()=>{
	console.log('3s后执行我')
},3000)

定时任务:

setInterval(()=>{
		console.log('hello')
},3000)

什么场景下要用定时任务?

(1)实时跟后端交互,基于http+定时任务(websocket协议:服务端主动推送消息,手机app的消息推送)

(2)秒杀场景,先提交秒杀请求,每隔3s,查询是否秒到;

代码展示

<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <title>Title</title>
   <script src="./js/vue.js"></script>
</head>
<body>
<div id="app">
   <h1>vue声明周期</h1>
   <button @click="handleShow">点我组件显示和消失</button>
   <hr>
   <child v-if="show"></child>
   <hr>
</div>
</body>
<script>
   // 定义一个全局组件
   Vue.component('child', {
       template: `
         <div>
         <button>后退</button>
         {{ title }}
         <button @click="handleClick">前进</button>
         </div>`,
       data() {
           return {
               title: '好看的首页',
               t:''
           }
       },
       methods: {
           handleClick() {
               // alert('前进')
               this.title = 'lqz'
           }
       },
       beforeCreate() {
           console.log('beforeCreate')
           console.log(this.$data)
           console.log(this.$el)
       },
       created() {
           console.log('created')
           console.log(this.$data)
           console.log(this.$el)
           // 开启定时器,每隔3s,打印hello
           this.t=setInterval(()=>{
               console.log('hello')
           },3000)
       },
       beforeMount() {
           console.log('beforeMount')
           console.log(this.$data)
           console.log(this.$el)
       },
       mounted() {
           console.log('mounted')
           console.log(this.$data)
           console.log(this.$el)
       },
       beforeUpdate() {
           console.log('beforeUpdate')
       },
       updated() {
           console.log('updated')
       },
       beforeDestroy() {
           console.log('当前状态:beforeDestroy')
       },
       destroyed() {
           console.log('当前状态:destroyed')
           // 销毁定时器
           clearInterval(this.t)
           this.t=null
       },
   })
   var vm = new Vue({
       el: '#app',
       data: {
           show: true
       },
       methods: {
           handleShow() {
               this.show = !this.show
           }
       }
   })
</script>
</html>

与后端交互

1.发展过程

2.代码展示

前端页面:

<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <title>Title</title>
   <script src="./js/vue.js"></script>
   <script src="https://unpkg.com/axios/dist/axios.min.js"></script>
   <script src="http://libs.baidu.com/jquery/2.0.0/jquery.min.js"></script>
</head>
<body>
<div id="app">
   <h1>jquery的ajax与后端交互</h1>
   <!--    <button @click="handleLoad1">点击加载数据</button>-->
   <!--    <br>-->
   <!--    <p>名字是:{{name}}</p>-->
   <!--    <p>年龄是:{{age}}</p>-->
   <!--    <hr>-->
   <h1>js原生的fetch与后端交互</h1>
   <!--    <button @click="handleLoad2">点击加载数据</button>-->
   <!--    <br>-->
   <!--    <p>名字是:{{name}}</p>-->
   <!--    <p>年龄是:{{age}}</p>-->
   <!--    <hr>-->
   <h1>axios与后端交互</h1>
   <button @click="handleLoad3">点击加载数据</button>
   <br>
   <p>名字是:{{name}}</p>
   <p>年龄是:{{age}}</p>
   <hr>
</div>
</body>
<script>
   var vm = new Vue({
       el: '#app',
       data: {
           name: '',
           age: 0
       },
       methods: {
           handleLoad1() {
               $.ajax({
                   url: "http://127.0.0.1:5000/",
                   type: 'get',
                   success: data => {
                       console.log(typeof data)
                       data = JSON.parse(data) // data 是字符串类型,需要转成对象类型
                      console.log(typeof data)
                       this.name = data.name
                       this.age = data.age
                   }
               })
           },
           handleLoad2() { // 用的很少
               fetch('http://127.0.0.1:5000/').then(res => res.json()).then(res => {
                   console.log(res)
                   console.log(typeof res)
                   this.name = res.name
                   this.age = res.age
               })
           },
           handleLoad3() { // 用的很少
               axios.get('http://127.0.0.1:5000/').then(res => {
                   console.log(res.data)  // 后端真正的数据在res.data中
                   this.name = res.data.name
                   this.age = res.data.age
               })
           },
       }
   })
</script>
</html>

后端Flask框架:

from flask import Flask, jsonify
app = Flask(__name__)
@app.route('/')
def index():
   res = jsonify({'name': 'lqz', 'age': 19})
   # 处理了跨域()  在响应头中加入 django写后端 {'Access-Control-Allow-Origin': '*'}
   res.headers = {'Access-Control-Allow-Origin': '*'}
   return res
if __name__ == '__main__':
   app.run()

电影案例

前端页面展示:

<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <title>Title</title>
   <script src="./js/vue.js"></script>
   <script src="https://unpkg.com/axios/dist/axios.min.js"></script>
</head>
<body>
<div id="app">
   <h1>电影小案例</h1>
   <ul>
       <li v-for="film in filmList">
           <h2>电影名:{{film.name}}</h2>
           <img :src="film.poster" alt="" height="400px" width="300px">
       </li>
   </ul>
</div>
</body>
<script>
   var vm = new Vue({
       el: '#app',
       data: {
           filmList: []
       },
       created() {
           axios.get('http://127.0.0.1:5000/films').then(res => {
               this.filmList = res.data.data.films
           })
       }
   })
</script>
</html>

后盾Flask框架:

from flask import Flask, jsonify
app = Flask(__name__)
@app.route('/films')
def films():
   with open('./film.json', 'r', encoding='utf-8') as f:
       data = json.load(f)
   res = jsonify(data)
   res.headers = {'Access-Control-Allow-Origin': '*'}
   return res
if __name__ == '__main__':
   app.run()

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