Javascript Vanilla functions

vanilla.js

function hasClass(el, className) {
    return el.classList ? el.classList.contains(className) : new RegExp('\\b' + className + '\\b').test(el.className);
}

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

function removeClass(el, className) {
    if (el.classList) el.classList.remove(className);
    else el.className = el.className.replace(new RegExp('\\b' + className + '\\b', 'g'), '');
}

function toggleClass(el, className){
    if(hasClass(el, className)) removeClass(el, className);
    else addClass(el, className);
}

function addEvent(el, type, handler) {
    if (el.attachEvent) el.attachEvent('on' + type, handler); else el.addEventListener(type, handler, false);
}

function removeEvent(el, type, handler) {
    if (el.detachEvent) el.detachEvent('on' + type, handler); else el.removeEventListener(type, handler, false);
}

function throttle(fn, threshhold, scope) {
    threshhold || (threshhold = 250);
    var last,
        deferTimer;
    return function () {
        var context = scope || this;

        var now = +new Date,
            args = arguments;
        if (last && now < last + threshhold) {
            // hold on to it
            clearTimeout(deferTimer);
            deferTimer = setTimeout(function () {
                last = now;
                fn.apply(context, args);
            }, threshhold);
        } else {
            last = now;
            fn.apply(context, args);
        }
    };
}