Saving URL parameters as cookies and adding to forms

param-cookes.js

/* 
This script will take the URL parameters of your choice and save them to cookies during a user session,
so if a user changes pages on your site, the data will still be submitted with your forms.

Be sure to include the JS Cookie plugin https://github.com/js-cookie/js-cookie and jquery.
Add the code below to your website footer.
Adjust variable, parameter, and form input names accordingly, add or remove as necessary.

Note: some servers block files with 'cookie' in the name. Be sure to change the filename if you have problems loading the script.

This code is based on Jenna Molby's tutorial:
http://jennamolby.com/how-to-use-cookies-to-capture-url-parameters/
*/

// Parse the URL
function getParameterByName(name) {
    name = name.replace(/[\[]/, "\\[").replace(/[\]]/, "\\]");
    var regex = new RegExp("[\\?&]" + name + "=([^&#]*)"),
        results = regex.exec(location.search);
    return results === null ? "" : decodeURIComponent(results[1].replace(/\+/g, " "));
}
// Give the URL parameters variable names
var source = getParameterByName('source');
var medium = getParameterByName('medium');
var campaign = getParameterByName('campaign');

// Set the cookies
if(Cookies.get('source') == null || Cookies.get('source') == "") {
Cookies.set('source', source);
}
if(Cookies.get('medium') == null || Cookies.get('medium') == "") {
Cookies.set('medium', medium);
}
if(Cookies.get('campaign') == null || Cookies.get('campaign') == "") {
Cookies.set('campaign', campaign);
}

// Grab the cookie value and set the form field values
$(document).ready(function(){
	$('input[name=source').val(source);
	$('input[name=medium').val(medium);
	$('input[name=campaign').val(campaign);
});