为什么REQ.BODY始终为空？

Question

I know there are a lot of answer already marked as a working solution, but I can't make it work in my case, so please don't marked it as already answered, this is my scenario:

AJAX CLIENT SIDE

var data ={};
data.test="ciaozio";
$.ajax({
    url: 'http://localhost:5000/dir',
    method: "POST",
    contentType: "application/json",
    data: JSON.stringify(data),
    header: "Access-Control-Allow-Origin",
    success: function(data){
        console.log(data);
    },
    error: function(data) {
        console.log("error");
    }
});

NODEJS SERVER-SIDE

var express = require('express');
var bodyParser = require('body-parser');
var app = express();
var router = express.Router();
app.use(bodyParser.urlencoded({ extended: true })); // support encoded bodies
app.use(bodyParser.json()); // support json encoded bodies
app.use('/', router);

app.post('/dir', function (req, res) {
  console.log(req.body);
  res.end("Ok");
})

var server = app.listen(5000, function () {
   var host = server.address().address
   var port = server.address().port
   console.log("Example app listening at http://%s:%s", host, port)
})

CONSOLE-OUTPUT

Example app listening at http://:::5000
{}

CLIENT-SIDE CONSOLE OUTPUT

Access to XMLHttpRequest at 'http://localhost:5000/dir' from origin 'null' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.
index.js:29 error
jquery-3.4.1.min.js:2 POST http://localhost:5000/dir net::ERR_FAILED

Answer 1

You need to add and configure CORS to your request.

Steps:

1.Install cors npm package

npm install cors

2.Node server-side snippt

 var express = require('express')
 var cors = require('cors')
 var app = express()
 app.use(cors())
 //app.use(...) lines;

// app.post(..) lines;