vue阻止重复请求实现示例详解

Vue
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2023-07-22
Vue组件实现原理详细分析
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标签   Vue实践
目录
  • 背景
  • 思路
  • 方式1-通过定时器做防抖处理
  • (a)概述
  • (b)代码
  • (c)预览
  • (d)存在的问题
  • 情况-在点击事件上做防抖
  • 情况-在接口方法做防抖
  • 方式2-通过取消ajax请求
  • (a) 概述
  • (b)原理
  • 原生ajax取消请求
  • axios取消请求
  • (c)代码
  • 步骤1-通过axios请求拦截器取消重复请求
  • 步骤2-通过axios响应拦截器处理请求成功
  • 步骤3-通过axios响应拦截器处理请求失败

背景


项目当中前端代码会遇到同一个请求向服务器发了多次的情况,我们要避免服务器资源浪费,同一个请求一定时间只允许发一次请求

思路

(1)如果业务简单,例如同一个按钮防止多次点击,我们可以用定时器做防抖处理

(2)如果业务复杂,例如多个组件通过代码,同一个请求发多次,这个时候防抖已经不好处理了,最好是对重复的ajax请求统一做取消操作

方式1-通过定时器做防抖处理

(a)概述

效果:当用户连续点击多次同一个按钮,最后一次点击之后,过小段时间后才发起一次请求

原理:每次调用方法后都产生一个定时器,定时器结束以后再发请求,如果重复调用方法,就取消当前的定时器,创建新的定时器,等结束后再发请求,工作当中可以用第三方封装的工具函数例如lodash的debounce方法来简化防抖的代码

(b)代码

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=.0">
    <title>Document</title>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/lodash.js/4.17.21/lodash.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/vue/2.6.14/vue.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/axios/0.26.0/axios.min.js" type="application/javascript"></script>
</head>
<body>
    <div id="app">
        <button @click="onClick">请求</button>
    </div>
</body>
<script>
// 定义请求接口
function sendPost(data){
    return axios({
        url: 'https://nodejs-cloud-studio-demo-bkzxs.nodejs-cloud-studio-demo..cn-hangzhou.fc.devsapp.net/test',
        method: 'post',
        data
    })
}
new Vue({
    el: '#app',
    methods: {
        // 调用lodash的防抖方法debounce,实现连续点击按钮多次,.3秒后调用1次接口
        onClick: _.debounce(async function(){
            let res = await sendPost({username:'zs', age:})
            console.log('请求的结果', res.data)
        },),
    },
})
</script>
</html>

(c)预览

连接

(d)存在的问题

无法解决多个按钮件的重复请求的发送问题,例如下面两种情况

情况-在点击事件上做防抖

按钮事件间是相互独立的,调用的是不同方法,做不到按钮间防抖效果

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=.0">
    <title>Document</title>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/lodash.js/4.17.21/lodash.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/vue/2.6.14/vue.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/axios/0.26.0/axios.min.js" type="application/javascript"></script>
</head>
<body>
    <div id="app">
        <button @click="onClick" ref="btn1">请求1</button>
        <button @click="onClick" ref="btn2">请求2</button>
    </div>
</body>
<script>
let sendPost = function(data){
    return axios({
        url: 'http://nodejs-cloud-studio-demo-bkzxs.nodejs-cloud-studio-demo..cn-hangzhou.fc.devsapp.net/test',
        method: 'post',
        data
    })
}
new Vue({
    el: '#app',
    mounted() {
        this.$refs.btn.click()
        this.$refs.btn.click()
    },
    methods: {
        // 使用lodash对请求方法做防抖
        //这里有问题,只是对每个按钮的点击事件单独做了防抖,但是两个按钮之间做不到防抖的效果
        onClick: _.debounce(async function(){
            let res = await sendPost({username:'zs', age:})
            console.log('请求的结果', res.data)
        },),
        onClick: _.debounce(async function(){
            let res = await sendPost({username:'zs', age:})
            console.log('请求的结果', res.data)
        },),
    },
})
</script>
</html>

预览

情况-在接口方法做防抖

按钮间调用的方法是相同的,是可以对方法做防抖处理,但是处理本身对方法做了一次封装,会影响到之前方法的返回值接收,需要对之前的方法做更多处理,变得更加复杂,不推荐

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=.0">
    <title>Document</title>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/lodash.js/4.17.21/lodash.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/vue/2.6.14/vue.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/axios/0.26.0/axios.min.js" type="application/javascript"></script>
</head>
<body>
    <div id="app">
        <button @click="onClick" ref="btn1">请求1</button>
        <button @click="onClick" ref="btn2">请求2</button>
    </div>
</body>
<script>
// 使用lodash对请求方法做防抖,    
let sendPost = _.debounce(function(data){
    //这里有问题,这里的返回值不能作为sendPost方法执行的返回值,因为debounce内部包裹了一层
    return axios({
        url: 'http://nodejs-cloud-studio-demo-bkzxs.nodejs-cloud-studio-demo..cn-hangzhou.fc.devsapp.net/test',
        method: 'post',
        data
    })
},)
new Vue({
    el: '#app',
    mounted() {
        this.$refs.btn.click()
        this.$refs.btn.click()
    },
    methods: {
        onClick: async function(){
            //这里有问题,sendPost返回值不是promise,而是undefined
            let res = await sendPost({username:'zs', age:})
            console.log('请求的结果', res)
        },
        onClick: async function(){
            let res = await sendPost({username:'zs', age:})
            console.log('请求的结果', res)
        },
    },
})
</script>
</html>

预览

方式2-通过取消ajax请求

(a) 概述

直接对请求方法做处理,通过ajax库的api方法把重复的请求给取消掉

(b)原理

原生ajax取消请求

通过调用XMLHttpRequest对象实例的abort方法把请求给取消掉

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=.0">
    <title>Document</title>
</head>
<body>
</body>
<script>
//原生ajax的语法    
let xhr = new XMLHttpRequest();
xhr.open("GET", "http://nodejs-cloud-studio-demo-bkzxs.nodejs-cloud-studio-demo..cn-hangzhou.fc.devsapp.net/test?username=zs&age=20", true);
xhr.onload = function(){
    console.log(xhr.responseText)
}
xhr.send();
//在谷歌浏览器的低速g下面测试
//通过XMLHttpRequest实例的abort方法取消请求
setTimeout(() => xhr.abort(),);
</script>
</html>

预览

axios取消请求

通过axios的CancelToken对象实例cancel方法把请求给取消掉

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=.0">
    <title>Document</title>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/axios/0.26.0/axios.min.js" type="application/javascript"></script>
</head>
<body>
</body>
<script>
/*axios的取消的语法*/
// 方式-通过axios.CancelToken.source产生cancelToken和cancel方法
/*
const source =  axios.CancelToken.source();
axios.get('http://nodejs-cloud-studio-demo-bkzxs.nodejs-cloud-studio-demo..cn-hangzhou.fc.devsapp.net/test', {
    params: {username: 'zs', age:}, 
    cancelToken: source.token
}).then(res=>{
    console.log('res', res.data)
}).catch(err=>{
    console.log('err', err)
})
//在谷歌浏览器的低速g下面测试
//通过调用source的cancel方法取消
setTimeout(() => source.cancel(),);
*/
/**/
// 方式-通过new axios.CancelToken产生cancelToken和cancel方法
let cancelFn 
const cancelToken =  new axios.CancelToken(cancel=>{
    cancelFn = cancel
});
axios.get('http://nodejs-cloud-studio-demo-bkzxs.nodejs-cloud-studio-demo..cn-hangzhou.fc.devsapp.net/test', {
    params: {username: 'zs', age:}, 
    cancelToken: cancelToken
}).then(res=>{
    console.log('res', res.data)
}).catch(err=>{
    console.log('err', err)
})
//在谷歌浏览器的低速g下面测试
//通过调用cancelFn方法取消
setTimeout(() => cancelFn(),);
</script>
</html>

预览

(c)代码

步骤1-通过axios请求拦截器取消重复请求

通过axios请求拦截器,在每次请求前把请求信息和请求的取消方法放到一个map对象当中,并且判断map对象当中是否已经存在该请求信息的请求,如果存在取消上传请求

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=.0">
    <title>Document</title>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/vue/2.6.14/vue.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/axios/0.26.0/axios.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/qs/6.10.3/qs.js" type="application/javascript"></script>
</head>
<body>
    <div id="app">
        <button @click="onClick" ref="btn1">请求1</button>
        <button @click="onClick" ref="btn2">请求2</button>
    </div>
</body>
<script>
//存储请求信息和取消方法的的map对象    
const pendingRequest = new Map();  
//根据请求的信息(请求方式,url,请求get/post数据),产生map的key
function getRequestKey(config){
    const { method, url, params, data } = config;
    return [method, url, Qs.stringify(params), Qs.stringify(data)].join("&");
}   
//请求拦截器
axios.interceptors.request.use(
    function (config) {
    //根据请求的信息(请求方式,url,请求get/post数据),产生map的key
    let requestKey = getRequestKey(config)
    //判断请求是否重复
    if(pendingRequest.has(requestKey)){
        //取消上次请求
        let cancel = pendingRequest.get(requestKey)
        cancel()
        //删除请求信息
        pendingRequest.delete(requestKey) 
    }
    //把请求信息,添加请求到map当中
    // 生成取消方法
    config.cancelToken = config.cancelToken || new axios.CancelToken(cancel => {
        // 把取消方法添加到map
        if (!pendingRequest.has(requestKey)) {
            pendingRequest.set(requestKey, cancel)
        }
    })
    return config;
  },
  (error) => {
     return Promise.reject(error);
  }
);
let sendPost = function(data){
    return axios({
        url: 'http://nodejs-cloud-studio-demo-bkzxs.nodejs-cloud-studio-demo..cn-hangzhou.fc.devsapp.net/test',
        method: 'post',
        data
    })
}
new Vue({
    el: '#app',
    mounted() {
        this.$refs.btn.click()
        this.$refs.btn.click()
    },
    methods: {
        // 使用lodash对请求方法做防抖
        //这里有问题,只是对每个按钮的点击事件单独做了防抖,但是两个按钮之间做不到防抖的效果
        onClick: async function(){
            let res = await sendPost({username:'zs', age:})
            console.log('请求的结果', res.data)
        },
        onClick: async function(){
            let res = await sendPost({username:'zs', age:})
            console.log('请求的结果', res.data)
        },
    },
})
</script>
</html>

预览

步骤2-通过axios响应拦截器处理请求成功

通过axios的响应拦截器,在请求成功后在map对象当中,删除该请求信息的数据

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=.0">
    <title>Document</title>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/vue/2.6.14/vue.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/axios/0.26.0/axios.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/qs/6.10.3/qs.js" type="application/javascript"></script>
</head>
<body>
    <div id="app">
        <button @click="onClick" ref="btn1">请求1</button>
        <button @click="onClick" ref="btn2">请求2</button>
    </div>
</body>
<script>
//存储请求信息和取消方法的的map对象    
const pendingRequest = new Map();  
//根据请求的信息(请求方式,url,请求get/post数据),产生map的key
function getRequestKey(config){
    const { method, url, params, data } = config;
    return [method, url, Qs.stringify(params), Qs.stringify(data)].join("&");
}   
//请求拦截器
axios.interceptors.request.use(
    function (config) {
    //根据请求的信息(请求方式,url,请求get/post数据),产生map的key
    let requestKey = getRequestKey(config)
    //判断请求是否重复
    if(pendingRequest.has(requestKey)){
        //取消上次请求
        let cancel = pendingRequest.get(requestKey)
        cancel()
        //删除请求信息
        pendingRequest.delete(requestKey) 
    }
    //把请求信息,添加请求到map当中
    // 生成取消方法
    config.cancelToken = config.cancelToken || new axios.CancelToken(cancel => {
        // 把取消方法添加到map
        if (!pendingRequest.has(requestKey)) {
            pendingRequest.set(requestKey, cancel)
        }
    })
    return config;
  },
  (error) => {
     return Promise.reject(error);
  }
);
//响应拦截器
axios.interceptors.response.use(
  (response) => {
        //请求成功
        //删除请求的信息
        let requestKey = getRequestKey(response.config)
        if(pendingRequest.has(requestKey)){
            pendingRequest.delete(requestKey)   
        }
        return response;
   },
   (error) => {
        return Promise.reject(error);
   }
);
let sendPost = function(data){
    return axios({
        url: 'http://nodejs-cloud-studio-demo-bkzxs.nodejs-cloud-studio-demo..cn-hangzhou.fc.devsapp.net/test',
        method: 'post',
        data
    })
}
new Vue({
    el: '#app',
    mounted() {
        this.$refs.btn.click()
        this.$refs.btn.click()
    },
    methods: {
        // 使用lodash对请求方法做防抖
        //这里有问题,只是对每个按钮的点击事件单独做了防抖,但是两个按钮之间做不到防抖的效果
        onClick: async function(){
            let res = await sendPost({username:'zs', age:})
            console.log('请求的结果', res.data)
        },
        onClick: async function(){
            let res = await sendPost({username:'zs', age:})
            console.log('请求的结果', res.data)
        },
    },
})
</script>
</html>

预览

步骤3-通过axios响应拦截器处理请求失败

通过axios的响应拦截器,在请求失败后在map对象当中,删除该请求信息的数据

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=.0">
    <title>Document</title>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/vue/2.6.14/vue.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/axios/0.26.0/axios.min.js" type="application/javascript"></script>
    <script src="https://lf-cdn-tos.bytecdntp.com/cdn/expire-1-M/qs/6.10.3/qs.js" type="application/javascript"></script>
</head>
<body>
    <div id="app">
        <button @click="onClick" ref="btn1">请求1</button>
        <button @click="onClick" ref="btn2">请求2</button>
    </div>
</body>
<script>
//存储请求信息和取消方法的的map对象    
const pendingRequest = new Map();  
//根据请求的信息(请求方式,url,请求get/post数据),产生map的key
function getRequestKey(config){
    const { method, url, params, data } = config;
    return [method, url, Qs.stringify(params), Qs.stringify(data)].join("&");
}   
//请求拦截器
axios.interceptors.request.use(
    function (config) {
    //根据请求的信息(请求方式,url,请求get/post数据),产生map的key
    let requestKey = getRequestKey(config)
    //判断请求是否重复
    if(pendingRequest.has(requestKey)){
        //取消上次请求
        let cancel = pendingRequest.get(requestKey)
        cancel()
        //删除请求信息
        pendingRequest.delete(requestKey) 
    }
    //把请求信息,添加请求到map当中
    // 生成取消方法
    config.cancelToken = config.cancelToken || new axios.CancelToken(cancel => {
        // 把取消方法添加到map
        if (!pendingRequest.has(requestKey)) {
            pendingRequest.set(requestKey, cancel)
        }
    })
    return config;
  },
  (error) => {
     return Promise.reject(error);
  }
);
//删除请求信息
function delPendingRequest(config){
    let requestKey = getRequestKey(config)
    if(pendingRequest.has(requestKey)){
        pendingRequest.delete(requestKey)   
    } 
}
//响应拦截器
axios.interceptors.response.use(
  (response) => {
        //请求成功
        //删除请求的信息
        delPendingRequest(response.config)
        return response;
   },
   (error) => {
        //请求失败
        //不是取消请求的错误
        if (!axios.isCancel(error)){
            //服务器报,500报错,删除请求信息
            delPendingRequest(error.config || {})
        } 
        return Promise.reject(error);
   }
);
let sendPost = function(data){
    return axios({
        url: 'http://nodejs-cloud-studio-demo-bkzxs.nodejs-cloud-studio-demo..cn-hangzhou.fc.devsapp.net/test',
        method: 'post',
        data
    })
}
new Vue({
    el: '#app',
    mounted() {
        this.$refs.btn.click()
        this.$refs.btn.click()
    },
    methods: {
        // 使用lodash对请求方法做防抖
        //这里有问题,只是对每个按钮的点击事件单独做了防抖,但是两个按钮之间做不到防抖的效果
        onClick: async function(){
            let res = await sendPost({username:'zs', age:})
            console.log('请求的结果', res.data)
        },
        onClick: async function(){
            let res = await sendPost({username:'zs', age:})
            console.log('请求的结果', res.data)
        },
    },
})
</script>
</html>

预览

Vue组件实现原理详细分析
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