collect multiple inputs file to append to FormData

问题

Suppose I have the following form.

<form id="testForm">
  <input type="file" name="uploads[]"><br/>
  <input type="file" name="uploads[]"><br/>
  <input type="file" name="uploads[]"><br/>
  <input type="submit">
</form>

And this is part of the submit code which tries to collect files to append to FormData, but I don't know how to do it properly.

var formData = new FormData();

var fileList = $("input[name='uploads[]']");
for(var x = 0; x < fileList.length; x++) {
  formData.append('file'+x, ???);
  console.log('appended a file');
}

var request = new XMLHttpRequest();
request.open('POST', '/upload');
request.send(formData);

request.onload = function(e) {
  console.log('Request Status', request.status);
};

This is the server code.

app.post('/upload', function(req, res) {
  var form = new formidable.IncomingForm();
  form.parse(req, function(err, fields, files) {
    console.log('handling form upload - fields', fields);
    console.log('handling form upload - files', files);
  });
  res.send('Thank you');
});

If it works, I expect to see output and files saved in /tmp.

回答1:

You don't have to collect fields since you can put the form itself into FormData object:

var form = document.getElementById('testForm');

form.addEventListener('submit', function(e) {

  e.preventDefault();

  var request = new XMLHttpRequest();
  request.open('POST', '/upload');

  request.onload = function(e) {
    console.log('Request Status', request.status);
  };

  var formData = new FormData(form);
  request.send(formData);
});

UPDATE

If you need to upload several files, you might use multiple attribute on the input instead of several inputs:

<form id="testForm">
  <input type="file" name="upload" multiple>
  <input type="submit">
</form>

来源：https://stackoverflow.com/questions/51888112/collect-multiple-inputs-file-to-append-to-formdata