Question

I’ve seen websites where there is a box for the user to browse a file to upload, then an “Add more files” link. When the user clicks on the link, another box shows up, allowing the user to chose another file. And the user can click “Add more files” to keep adding boxes. How do they do this?

I’m using Ruby on Rails as my backend.

Answer 1

<div id="filePickers">
  <input type="file" name="files[]">
  <input type="file" name="files[]">
  <input type="file" name="files[]">
</div>

That will appear as an array of files on params[:files] when posted to your server.

If you want more, bind some Javascript to a button somewhere to add new inputs.

// jQuery for brevity
$('#filePickers').append('<input type="file" name="files[]">');