updateUrlQuery.js

var updateUrlQuery = function(url, key, value) {
    var query = key + '=' + value;
    var search = '';
    var hash = '';

    var hashIndex = url.indexOf('#');
    if (hashIndex > -1) {
        hash = url.substring(hashIndex);
        url = url.substring(0, hashIndex);
    }

    var queryIndex = url.indexOf('?');
    if (queryIndex > -1) {
        search = url.substring(queryIndex);
        url = url.substring(0, queryIndex);
    }
    
    if (!search) {
        return url + '?' + query + hash;
    }

    var reg = new RegExp('([?&])' + key + "(=[^&]+)?", 'g');
    if (reg.test(search)) {
        reg.lastIndex = 0;
        search = search.replace(reg, "$1" + query);
        return url + search + hash;
    }

    return url + search + '&' + query + hash;
};