Add Google Tag Script Function

addgoogletag.js

function addGoogleTrackingCode(trackingCode){
  var s = document.createElement("script");
    s.type = "text/javascript";
    s.src = "https://www.googletagmanager.com/gtag/js?id=" + trackingCode;
    s.setAttribute('async','');
    $("head").append(s);

  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());

  gtag('config', trackingCode);
}