How to setup a jQuery Ajax request to upload file(s)

jQueryAjaxUpload.js

var fileField = document.getElementById("file_picker");
var file = fileField.files[0]; // Use multiple attr in your input field to upload more than one file
var formData = new FormData();
formData.append('filecsv', file, file.name);

$.ajax({
  	type: "POST",
  	url: "",
  	processData: false,
  	contentType: false,
  	dataType: 'text',
  	data: formData,
})
.done(function(data) {
	// do stuff
});