function hasClass(elem, className) {
    return new RegExp(' ' + className + ' ').test(' ' + elem.className + ' ');
}

function addClass(elem, className) {
    if (!hasClass(elem, className)) {
        elem.className += ' ' + className;
    }
}

function removeClass(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, '');
    }
}

function toggleClass(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, '');
    } else {
        elem.className += ' ' + className;
    }
}

/* Usage Examples */

if(hasClass(myElem, 'some-class')) {
  // do something here
}

addClass(myElem, 'some-class');

removeClass(myElem, 'some-class');
toggleClass(myElem, 'some-class');