How to implement react backend request data

React backend request data implementation method: 1. Configure ""proxy":"http://localhost:5000"" in package.json; 2. Create "setupProxy.js" in the src directory " file; 3. Call the function configured in "setupProxy.js", the code is such as "createProxyMiddleware('/api2',{target:...}".

The operating environment of this tutorial: Windows 10 system, react version 18.0.0, Dell G3 computer.

How to request data from the react backend?

react -ajax request background data method

##react-ajax

axios

Method 1: Configure

 "proxy":"http://localhost:5000"

in package.json so that localhost:5000 is the server we want to proxy to

  getStudentData = () => {
    axios.get('/students').then(
      (result) => { console.log(result.data); },
      (reason) => { console.log(reason); })
  }

Get the data of /students in
• localhost:5000

**Advantages: **Simple configuration, front-end request resources are not required Any prefix required

**Disadvantage: **Cannot configure multiple proxy servers

Method 2: Create the setupProxy.js file in the src directory

• Step one: webpack is configured to call the function configured in setupProxy.js

• setupProxy.js

• Step 2: Configuration

//const proxy=require("http-proxy-middleware")   :视频中请求的包，引用它出现了无法访问的问题//应该使用以下写法*******const { createProxyMiddleware } = require("http-proxy-middleware");module.exports=function(app){
    app.use(
        createProxyMiddleware('/api1',{//遇见/api1前缀的请求，就会触发该代理配置
            target:"http://localhost:5000",//请求转发给谁
            changeOrigin:true,//控制服务器收到的请求头中Host字段的值：host就是主机名+端口号
            	//true:后端接收到的host：localhost:5000
            	//false:后端接收到的host：localhost:3000
            	//系统默认为false，一般会设为true
            pathRewrite:{"^/api1":""}//重写请求路径（必须要写）
            //不写：后台接收到的请求路径：/api1/student
            //写了：后台请求的路径：/student
        }),
        createProxyMiddleware('/api2',{
            target:"http://localhost:5001",
            changeOrigin:true,
            pathRewrite:{"^/api2":""}
        }),
    )}

Solution link: https://www.csdn.net/tags/OtTaIg0sNzE3OC1ibG9n.html

Cross-domain request real interface case

• App.jsx

import React, { Component } from 'react'
import Search from './components/Search'
import List from './components/List'
import './App.css'

export default class App extends Component {
state={users:[]}
getSearchResult=(result)=>{
  this.setState({users:result})
}

  render() {
    return (
      <div>
        <search></search>
        <list></list>
      </div>
    )
  }
}

Search.jsx

import React, { Component } from 'react'
import axios from 'axios'
import './index.css'

export default class Search extends Component {

  search = () => {
    //获取输入框中的值
    const { value } = this.keyWordElement;
    //发送请求
    axios.get(`/api1/search/users?q=${value}`).then(
      result => {
        this.props.getSearchResult(result.data.items)
      },
      reason => {
        console.log(reason);
      })
  }



  render() {
    return (
      <section>
        <h3 id="搜索github用户">搜索github用户</h3>
        <div>
          <input> this.keyWordElement = c} type="text" placeholder="enter the name you search" /> <button>搜索</button>
        </div>
      </section>
    )
  }
}

List.jsx

import React, { Component } from 'react'

import './index.css'
export default class List extends Component {
  render() {
    return (
      <div>
        {this.props.users.map(item=>{
            return    <div>
                <a>
                  <img  src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/020/8311c35cd4729255aa36862f92c15493-0.png" class="lazy" alt="How to implement react backend request data" >
                </a>
                <p>{item.login}</p>
              </div>
        })}
  
       
      </div>  
    )
  }
}

react-Communication between any components

Message subscription and publishing mechanism

PubSubJs：

##pub:( publish) publish

• sub:(subscribe) subscribe

pubsub-js

: It is used to implement publish and subscribe. You can see it in vue. eventBus, regarded as the carrier of the function

Subscriber: Create a function and pass this function to pubsub for hosting

• var token=PubSub.subscribe("myTopic",myFunction[托管的函数])//token，是当前订阅函数的唯一id，可以用来取消订阅
Publisher: Publishing means to realize the function of passing parameters or performing operations by calling the function specified by the subscriber

• PubSub.publish('myTopic','需要发送给订阅者的内容')

Step 1

: Add pubsub-js

yarn add pubsub-js

• **Step 2:**In Import

import PubSub from 'pubsub-js'

• into the component **Step 3: **Call the PubSub subscription function (usually subscribed in the componentDidMount hook function)

  componentDidMount(){
    this.token=PubSub.subscribe("changeState",this.changeStateObj)
  }

demo

List.jsx

import React, { Component } from 'react'
import PubSub from 'pubsub-js'
import './index.css'
export default class List extends Component {
  state={
    users:[],//拿到的用户信息
    isFirst:true,//是否第一次访问
    isLoading:false,//是否正在加载
    err:"",//返回的错误信息
  
  }

  changeStateObj=(msg,value)=>{
    this.setState(value)
  }

  componentDidMount(){
    this.token=PubSub.subscribe("changeState",this.changeStateObj)
  }
  componentWillUnmount(){
    PubSub.unsubscribe(this.token)
  }
 
  render() {
    let {users,isFirst,isLoading,err}=this.state
    return (
      

        {
          isFirst?
输入搜索内容搜索用户
:
          isLoading?
Loading...
:
          err?
{err}
:
        
          users.map(item=>{
            return    

                
                  
                
                
{item.login}
              
        })}
  
       
      
  
    )
  }
}

Search. jsx

import React, { Component } from 'react'
import axios from 'axios'
import './index.css'
import PubSub from 'pubsub-js'

export default class Search extends Component {
  

  search = () => {
    //获取输入框中的值
    const { value } = this.keyWordElement;
    PubSub.publish('changeState',{isFirst:false,isLoading:true})
    //发送请求
    axios.get(`/api1/search/users2?q=${value}`).then(
      result => {
        PubSub.publish('changeState',{isLoading:false,users:result.data.items})

      },
      reason => {
        PubSub.publish('changeState',{isLoading:false,err:reason.message})

      })
  }



  render() {
    return (
      <section>
        <h3 id="搜索github用户">搜索github用户</h3>
        <div>
          <input> this.keyWordElement = c} type="text" placeholder="enter the name you search" /> <button>搜索</button>
        </div>
      </section>
    )
  }
}

App.jsx

import React, { Component } from 'react'
import Search from './components/Search'
import List from './components/List'
import './App.css'

export default class App extends Component {



  render() {
    return (
      <div>
        <search></search>
        <list></list>
      </div>
    )
  }
}

What are the ways to send ajax requests?

xhr:xmlHttpRequest: traditional ajax

• jQuery: encapsulated xhr
  • axios: encapsulated xhr
  **fetch (fetch)?* Built-in in window, no need to borrow third-party libraries, use it directly
• Disadvantages: It is not very useful at the moment, there is no request sending interceptor

xhr

fetch

Disadvantages
• : Low compatibility
Advantages
• : No need to use xhr, no need to install third-party libraries, native

##The best way to write fetch

let getData=async()=>{	
	try{
        let result=await fetch(url);
        let data=await result.json();
    }catch(error){
        console.log('请求错误',error)
    }
}

recommends learning: "react video tutorial"

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