Defer Loading Javascript & Css in pure javascript & PHP

Defer_loading_js_css.php

<?php
/*
*This library will be used for speeding up website using defer loading of javascript & Css
*Made in pure javascript
async - javascript will be executed while loading the page.
defer - javascript will be executed after loading the page.
*/

//To include in Header files
$deferJs  = "h1:{src:'/javascript/shop_general.js',async:1},h2:{src:'http://www.google-analytics.com/ga.js',async:1}";
$deferCss   = "h1:{media:'print',href:'/css/stylePrint.css'}";
//To include in Page files
$deferJs  .= "p1:{src:'/javascript/page_script.js',defer:1}";
$deferCss   .= "p1:{media:'all',href:'/css/stylethispage.css'}";
?>
<script type="text/javascript">
function deferLoading()
{
var css = {<?php echo isset($deferCss) ? $deferCss : ''; ?>};
var js = {<?php echo isset($deferJs) ? $deferJs : ''; ?>};
//css
loadcss(css);
//js
loadjs(js);
}
if (window.addEventListener)
  window.addEventListener("load", deferLoading, false);
else if (window.attachEvent)
  window.attachEvent("onload", deferLoading);
else window.onload = deferLoading;

function loadjs(js)
{
var s = document.getElementsByTagName('head')[0];
for(var key in js){
var ga = document.createElement('script'); ga.type = 'text/javascript';
 if (!js.hasOwnProperty(key)) continue;
var obj = js[key];
for (var prop in obj) { 
        if(!obj.hasOwnProperty(prop)) continue;
		switch(prop)
		{
		case 'src':
		ga.src = obj[prop]; break;
		case 'async':
		ga.async = true; break;
		case 'defer':
		ga.defer = true; break;
		}
    }
s.appendChild(ga);
}
}
  
function loadcss(css)
{
var s = document.getElementsByTagName('head')[0];
for(var key in css){
var l = document.createElement('link');
l.type = 'text/css';l.rel = 'stylesheet';
 if (!css.hasOwnProperty(key)) continue;
var obj = css[key];
for (var prop in obj) { 
        if(!obj.hasOwnProperty(prop)) continue;
		switch(prop)
		{
		case 'media':
		l.media = obj[prop]; break;
		case 'href':
		l.href = obj[prop]; break;
		}
    }
s.appendChild(l);
}
}
</script>