Node.js - enable cors cross-origin resource sharing in express

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cors cross-domain resource sharing

Cross-domain issues with interfaces

There is a serious problem in writing GET and POST interfaces: cross-domain requests are not supported

Example

routing module

const express = require('express')
const router = express.Router()
 
router.post('/post', (req, res) =>{
    const body = req.body
        res.send({
        status:0,
        msg:'POST 请求',
        data:body
    })
})
module.exports = router
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server side code

const express = require('express')
const app = express()

app.use(express.urlencoded({extended: false}))

const router = require('./apiRouter')
app.use('/api', router)

app.listen(80, ()=> {
    console.log('express 服务器运行在 http://127.0.0.1.80')
})
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test page

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.staticfile.org/jquery/1.10.0/jquery.min.js"></script>
</head>
<body>
    <button id="postBut"> POST </button>
   
   <script>
    $(function(){
            测试 POST 接口
            $('#postBut').on('click', function(){
                $.ajax({
                    type:'POST',
                    url:'http://127.0.0.1/api/post',
                    data:{name:'haimeimei', age: 18},
                    success: function(res){
                        console.log(res)
                    }
                })
            })
        })
    </script>
</body>
</html>
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When we click the POST button on the web page, the request is not successful, and the terminal will report an error (there is an interface cross-domain problem). Because the web page is opened through the file protocol ( file:///...), but the requested interface is the http protocol, and there are different protocols. As long as any one of the protocol, domain name, and port number is different, there is a cross-domain problem

Access link:

terminal error

A solution to the problem of interface cross-domain

corsMainstream solutions (recommended)
jsonpFlawed solution (only supports GET requests)

Use cors middleware to solve cross-domain problems

cors is a third-party middleware of Express. By installing and configuring cors middleware, cross-domain problems can be easily solved
The use steps are divided into three steps
- run npm install corsinstall middleware
- Use const cors = require('cors')import middleware
- call app.use(cors())configure

Example

The above code remains unchanged, only the server-side code needs to be changed, and the cors middleware must be configured before routing to solve the interface cross-domain problem

 const express = require('express')
 const app = express()
 
 app.use(express.urlencoded({extended: false}))
 
 // 配置 cors 这个中间件
 const cors = require('cors')
 app.use(cors())
 
 const router = require('./apiRouter')
 app.use('/api', router)
 
 app.listen(80, ()=> {
     console.log('express 服务器运行在 http://127.0.0.1.80')
 })
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Web terminal information