Parse.User.current() returns null - parse-platform

Question

We are trying to create a file upload system. We currently have a form in upload.ejs that allows the user to select a file and then the form calls upload.js which uses Parse's REST API to upload the file. In the success field of the REST API we are saving information about the file uploaded to our parse database. We would also like to save the information about the user uploading the file, but Parse.User.current() is returning null.
Our upload.js is saved in the public folder and the code is as follows:
$(function() {
var file;
$('#fileselect').bind("change", function(e) {
var files = e.target.files || e.dataTransfer.files;
// Our file var now holds the selected file
file = files[0];
});
$('#uploadbutton').click(function() {
var serverUrl = 'https://api.parse.com/1/files/' + file.name;
$.ajax({
type: "POST",
beforeSend: function(request) {
request.setRequestHeader("X-Parse-Application-Id", 'YOUR-APPLICATION-ID');
request.setRequestHeader("X-Parse-REST-API-Key", 'YOUR-REST-API-KEY');
request.setRequestHeader("Content-Type", file.type);
},
url: serverUrl,
data: file,
processData: false,
contentType: false,
success: function(data) {
//alert("File available at: " + data.url);
var Note = Parse.Object.extend("Note");
var note = new Note();
note.set("File Name", file.name); //change to user inputted file name
note.set("url", data.url);
//note.set("uploader", Parse.User.current());
console.log(Parse.User.current());
note.save();
var success = "<p>File Successfully Added. View it by clicking <a target='_blank' href="+data.url+">Here</a></p>";
$("#uploadMessage").addClass("uploadPadding");
$('#uploadMessage').append(success);
//TO DO: redirect off page
},
error: function(data) {
var obj = jQuery.parseJSON(data);
alert(obj.error);
}
});
});
});