Express body-parser req.body with formdata is empty object

问题

Somehow my req.body is always empty, maybe you have an idea:

here is my server code:

const Express = require('express');
const bodyParser = require('body-parser');

const app = new Express();
app.use(bodyParser.urlencoded({ extended: true }));
app.use(bodyParser.json());

app.post('/save', (req, res) => {
  console.log(req.body)  // => {}
  res.send(req.body);
});

const env = process.env.NODE_ENV || 'production';
app.listen(3000, err => {
   if (err) { return console.error(err); }
   console.info(`Server running on http://localhost:${port} [${env}]`);
});

When I try to send formdata with javascript the req.body is empty:

const data = new FormData(document.querySelector('form'));
console.log(data);  // seems empty already??? FormData{}??
const xhr = new XMLHttpRequest();
xhr.open('POST', 'http://localhost:3000/save');
xhr.send(data);

Same with postman:

I don’t understand this…

Sending x-www-form-urlencoded with postman or raw (application/json) works in postman. But sending the same headers with Formdata in javascript will still result in an empty object…

回答1:

To log every field in formData

let myForm = document.getElementById('myForm');
formData = new FormData(myForm);

for (let [key, value] of formData.entries()) { 
  console.log(key, value);
}

Fiddle - https://jsfiddle.net/thesumit67/j4znhxa5/1/

To handle it via express use multer. Here is an example - https://www.npmjs.com/package/multer

Make sure to add enctype="multipart/form-data" on form element. Otherwise Multer will ignore it.

let multer = require('multer');
let upload = multer();

app.post('/save', upload.fields([]), (req, res) => {
  console.log( req.body );
  console.log( req.files );
  res.sendStatus(200);
});

回答2:

From what I understand, the problem may be in the HTML form.

<form action="" method="POST">
 <input type="text" name="foo[bar]">
 <button>Submit</button>
</form>

Then in the server code it may look something like this.

 app.post('/save', (req, res) => {
 console.log(req.body.foo)  // => {}
 res.send(req.body.foo);
});

Again, this post is older so you've probably already fixed it.

回答3:

body-parser is deprecated and isn't a part of Express anymore.

Also, body-parser does not provide the functionality to parse form-data post data.

From the body-parser repository description:

This does not handle multipart bodies, due to their complex and typically large nature. For multipart bodies, you may be interested in the following modules:

• busboy and connect-busboy
• multiparty and connect-multiparty
• formidable
• multer

来源：https://stackoverflow.com/questions/44861517/express-body-parser-req-body-with-formdata-is-empty-object