Multer not accepting files in array format gives 'Unexpected File Error'

Question

Multer is a module used along with node js and express to upload files. I am using ng-file upload module on the angular side.

When I am sending multiple files one b

Answer 1

If someone is facing a similar issue when uploading a custom form data object, you can use this approach. In here I am not using ngFileUpload.

Client Side code

var fd = new FormData();

for( var i =0; i< files.length ; i++ ){
    fd.append('fileItems' , files[i] );
}

fd.append('_id', params._id );              
fd.append('user', params.user );              

return $http.post( ROOT_URL + '/uploadFiles/', fd, {
    transformRequest: angular.identity,
    headers: {'Content-Type': undefined }
});

Express Router

var multer  = require("multer");
var upload = multer({ dest: "uploads/" });

app.post('/api/uploadFiles', upload.array('fileItems'), handlers.files.uploadFiles);

Answer 2

The reason for the error is that multer currently does not support the array syntax that ng-file-upload uses by default which is files[0], files[1], files[2], etc. multer is expecting a series of files with the same field name.

The easiest solution is to set ng-file-upload's arrayKey option like so to avoid appending the [index] part:

Upload.upload({
  url: '/api/data/addtweet',
  arrayKey: '', // default is '[i]'
  data: {
    files: files
  }
})