jQueryでGoogle Analyticsのイベントトラッキングの簡単な設定方法

<!-- Global site tag (gtag.js) - Google Analytics --> 
<script async src="https://www.googletagmanager.com/gtag/js?id=GA_TRACKING_ID"></script> 
<script>
 window.dataLayer = window.dataLayer || []; 
 function gtag(){dataLayer.push(arguments);} 
 gtag('js', new Date()); 

 gtag('config', 'GA_TRACKING_ID'); 
</script>

<!-- Google Analytics --> 
<script> (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ 
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), 
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) 
})(window,document,'script','https://www.google-analytics.com/analytics.js','ga'); 

ga('create', 'UA-TRACKING-ID', 'auto'); 
ga('send', 'pageview'); 
</script> 
<!-- End Google Analytics -->

<script>
/* gtag.jsイベントトラッキング */
$(function() {
  $('a').click(function(e) {
    var ahref = $(this).attr('href');
    if(ahref.indexOf('WEBサイトURL') != -1 || ahref.indexOf('http') == -1 ) {
      ga('send','event','inlink','<?php echo 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']; ?>',ahref);
    }else{
      ga('send','event','outlink','<?php echo 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']; ?>',ahref);
    }
  });
});
</script>