Get and store a specific URL query param

getParam.js

<script type="text/javascript">
function setCookie(name, value, days){
    var date = new Date();
    date.setTime(date.getTime() + (days*24*60*60*1000)); 
    var expires = "; expires=" + date.toGMTString();
    document.cookie = name + "=" + value + expires + ";path=/";
}
function getParam(p){
    var match = RegExp('[?&]' + p + '=([^&]*)').exec(window.location.search);
    return match && decodeURIComponent(match[1].replace(/\+/g, ' '));
}
var gclid = getParam('gclid');
if(gclid){
    var gclsrc = getParam('gclsrc');
    if(!gclsrc || gclsrc.indexOf('aw') !== -1){
	    setCookie('gclid', gclid, 90);
	}
}
</script>