class-handlers.js

// Check if an element has a class
var hasClass = function (elem, className) {
    return new RegExp(' ' + className + ' ').test(' ' + elem.className + ' ');
}

// Add a class to an element
var addClass = function (elem, className) {
    if (!hasClass(elem, className)) {
        elem.className += ' ' + className;
    }
}

// Remove a class from an element
var removeClass = function (elem, className) {
    var newClass = ' ' + elem.className.replace( /[\t\r\n]/g, ' ') + ' ';
    if (hasClass(elem, className)) {
        while (newClass.indexOf(' ' + className + ' ') >= 0 ) {
            newClass = newClass.replace(' ' + className + ' ', ' ');
        }
        elem.className = newClass.replace(/^\s+|\s+$/g, '');
    }
}

// Toggle a class on an element
var toggleClass = function (elem, className) {
    if ( hasClass(elem, className) ) {
        removeClass(elem, className);
    }
    else {
        addClass(elem, className);
    }
}