query-params.js

function replaceUrl(key, newValue) {
    var url = window.location.href, 
        separator = ~url.indexOf('?') ? '&' : '?', 
        re = new RegExp('([?&])' + key + '=(.*?)([?&]|$)', 'i'), 
        match = re.exec(url), 
        hasParam = !!match;
    
    if (hasParam) {
        if (match[2] === newValue || !newValue) {
            return url.replace(re, '');
        }
        return url.replace(re, '$1' + key + '=' + newValue + '$3');
    }
    
    return url + separator + key + '=' + (newValue || '1');
}

function toggle(key, newValue) {
    window.location.href = replaceUrl(key, newValue);
}