JS urlFor

url_for.js

urlFor = function(url, params)
{
    url = url || window.location.href || '';

    url =  url.match(/\?/) ? url : url + '?';

    for (var key in params) {
        var re1 = RegExp( '\\?' + key + '=[^\&$]*(&|$)', 'g' );
        var re2 = RegExp( '\&' + key + '=[^\&$]*(&|$)', 'g' );
        var replacement = params[key] ? key + '=' + params[key] : "";
        
        
        if (re1.test(url)) {
            url = url.replace(re1, '?' + replacement + '&')
        }
        else if (re2.test(url)) {
            url = url.replace(re2, '&' + replacement  + '&')
        }
        else {
            url += '&' + replacement;
        }
    }
    if (url.indexOf("?", url.length - 1) !== -1) {
        url = url.substring(0, url.length - 1)
    }
    // cleanup url
    url = url.replace(/\&*$/g, '');
    url = url.replace(/\?\&*/g, '?');
    url = url.replace(/[&]{2}/g, '&');
    url = url.replace(/\?$/g, '');
    return url;
};