jQuery get URL query string

function getUrlPars()
{
    var vars = [], hash;
    var hashes = window.location.href.slice(window.location.href.indexOf('?') + 1).split('&');
    for(var i = 0; i < hashes.length; i++)
    {
        hash = hashes[i].split('=');
        vars.push(hash[0]);
        vars[hash[0]] = hash[1];
    }
    return vars;
}
var asin = getUrlPars()["asin"];
if(asin!='' && asin!=null){
    old_id = jQuery('#cst-btn').attr('href');
    jQuery('#cst-btn').attr('href', old_id+'?asin='+asin+'&channel=unknownChannel-thankyou')
}