Node.js multer Error: Unexpected field

Question

I have trouble with Node.js multer ...

I want to know what causes this problem. I think I set the right name of input[name=streamfile] between client and node.js's multer upload.single('streamfile').

I have no idea what other elements cause this problem.

Here is my code below.. Thanks.

Error Msg

Error: Unexpected field
    at makeError (/Users/taeseongpark/Documents/Study/NodeJS/node_basic_test/node_modules/multer/lib/make-error.js:12:13)
    at wrappedFileFilter (/Users/taeseongpark/Documents/Study/NodeJS/node_basic_test/node_modules/multer/index.js:40:19)
    at Busboy.<anonymous> (/Users/taeseongpark/Documents/Study/NodeJS/node_basic_test/node_modules/multer/lib/make-middleware.js:114:7)
    at emitMany (events.js:127:13)
    at Busboy.emit (events.js:201:7)
    at Busboy.emit (/Users/taeseongpark/Documents/Study/NodeJS/node_basic_test/node_modules/busboy/lib/main.js:38:33)
    at PartStream.<anonymous> (/Users/taeseongpark/Documents/Study/NodeJS/node_basic_test/node_modules/busboy/lib/types/multipart.js:213:13)
    at emitOne (events.js:96:13)
    at PartStream.emit (events.js:188:7)
    at HeaderParser.<anonymous> (/Users/taeseongpark/Documents/Study/NodeJS/node_basic_test/node_modules/dicer/lib/Dicer.js:51:16)

Client HTML

<form action="http://localhost:8989/fileupload" method="post" enctype="multipart/form-data">
    <input type="file" name="streamfile">
    <input type="button" data-inline="true" value="Input" id="filesubmit">
</form>
<script lang="javascript">
    $('form #filesubmit').on('click', (e)=>{
        var uploadfile = $("input[name=streamfile]")[0].files[0];
        var formData = new FormData(); 
        formData.append("myfile", uploadfile);

        console.log('uploadfile', uploadfile, uploadfile.type);

        var localurl = 'http://localhost:8989/fileupload'
        $.ajax({ 
            url: localurl,  // googleCloud
            data: formData, 
            processData: false, 
            contentType: false, 
            type: 'POST', 
            success: function(data){ 
                console.log('response data', data);
            } 
        });
    });
</script>

Node.js Server

var express = require('express')
var multer  = require('multer')
var upload = multer({ dest: 'uploads/' })

var app = express()

app.use(function(req, res, next) {
    res.header("Access-Control-Allow-Origin", "*");
    res.header("Access-Control-Allow-Headers", 'Content-Type, Authorization, Content-Length, X-Requested-With');
    res.header("Access-Control-Allow-Methods", "PUT, POST, GET, OPTIONS, DELETE");
    next();
});

app.post('/fileupload', upload.single('streamfile'), function (req, res) {
    console.log('req.file', req.file);
  // req.file is the `avatar` file 
  // req.body will hold the text fields, if there were any 
})

// Connect to Web Server
var port = '8989';
app.listen(port, () => {
    console.log('[Express] fileupload started at %d port', port);
});
// "express": "^4.16.2", "multer": "^1.3.0",

Answer 1

The formData.append assigned field name needs to match the server's expected field name set for Multer.

formData.append("streamfile", uploadfile);

Answer 2

try following code in html remove all javascript code

<form action="http://localhost:8989/fileupload" method="post" enctype="multipart/form-data">
        <input type="file" name="streamfile">
        <input type="submit" data-inline="true" value="Input" id="filesubmit">
    </form>