Inline Upload

var uploader = new MultipleUpload(el, {
 uploadUrl: '/api/upload',
 autoUpload: true,
 onTaskComplete: function(task) {
 // Add attachment chip to the editor
 var chip = document.createElement('span');
 chip.className = 'attachment-chip';
 chip.textContent = task.name;
 attachmentArea.appendChild(chip);
 }
});

// Toolbar button triggers file dialog
attachBtn.addEventListener('click', function() {
 uploader.openFileDialog();
});

An uploader inside a form

The uploader sits alongside the other fields and transfers in the background, so pressing submit never waits on bytes. With hiddenFieldId the completed GUIDs are kept in a hidden input, and the form posts references instead of file content.

Guard the submit while uploads are running

Nothing stops a user submitting mid-upload, and the form would then post a partial list. Disable submit until the queue is idle, or check the state in the handler — a record saved without the attachment the user believed they added is a bug they will not notice until much later.