JavaScript: Class Management

add_class.js

function addClass(el, className) {
    if (el.classList)
        el.classList.add(className);
    else
        el.className += ' ' + className;
}

function removeClass(el, className) {
    if (el.classList)
        el.classList.remove(className);
    else
        el.className = el.className.replace(new RegExp('(^|\\b)' + className.split(' ').join('|') + '(\\b|$)', 'gi'), ' ');
}