UTM tracking with javascript for ActiveCampaign

ActiveCampaign UTM tracking with javascript

Code I added to all pages on the site to collect utm parameters ... let me know if you have a better version:

var urlParams;
if (window.location.search.indexOf('utm_source=') greater than (replace, youtube doesn't allow angled bracket) -1)
{
(window.onpopstate = function () {
var match,
pl = /\+/g, // Regex for replacing addition symbol with a space
search = /([^&=]+)=?([^&]*)/g,
decode = function (s) { return decodeURIComponent(s.replace(pl, " ")); },
query = window.location.search.substring(1);
cookieStr = '';
nowPreserve = new Date();
oneYear = 365*24*60*60*1000; // one year in milliseconds
thenPreserve = nowPreserve.getTime() + oneYear;
nowPreserve.setTime(thenPreserve);
expireTime = nowPreserve.toUTCString();

urlParams = {};
while (match = search.exec(query))
{
urlParams[decode(match[1])] = decode(match[2]);
document.cookie = decode(match[1])+'='+decode(match[2])+';expires='+expireTime+';domain='+document.domain;
}
})();
document.getElementsByName('field[19]')[0].value = urlParams["utm_source"];
document.getElementsByName('field[20]')[0].value = urlParams["utm_medium"];
document.getElementsByName('field[21]')[0].value = urlParams["utm_campaign"];
document.getElementsByName('field[22]')[0].value = urlParams["utm_term"];
document.getElementsByName('field[23]')[0].value = urlParams["utm_content"];
}
else
{
function getCookieValue(a) {
var b = document.cookie.match('(^|;)\\s*' + a + '\\s*=\\s*([^;]+)');
return b ? b.pop() : '';
}
document.getElementsByName('field[19]')[0].value = getCookieValue("utm_source");
document.getElementsByName('field[20]')[0].value = getCookieValue("utm_medium");
document.getElementsByName('field[21]')[0].value = getCookieValue("utm_campaign");
document.getElementsByName('field[22]')[0].value = getCookieValue("utm_term");
document.getElementsByName('field[23]')[0].value = getCookieValue("utm_content");
}