function keydown()

in Documents/assets/smoothscroll/smooth-scroll.js [376:469]
74 lines of code
36 McCabe index (conditional complexity)

function keydown(event) {

    var target   = event.target;
    var modifier = event.ctrlKey || event.altKey || event.metaKey ||
                  (event.shiftKey && event.keyCode !== key.spacebar);

    // our own tracked active element could've been removed from the DOM
    if (!document.body.contains(activeElement)) {
        activeElement = document.activeElement;
    }

    // do nothing if user is editing text
    // or using a modifier key (except shift)
    // or in a dropdown
    // or inside interactive elements
    var inputNodeNames = /^(textarea|select|embed|object)$/i;
    var buttonTypes = /^(button|submit|radio|checkbox|file|color|image)$/i;
    if ( event.defaultPrevented ||
         inputNodeNames.test(target.nodeName) ||
         isNodeName(target, 'input') && !buttonTypes.test(target.type) ||
         isNodeName(activeElement, 'video') ||
         isInsideYoutubeVideo(event) ||
         target.isContentEditable ||
         modifier ) {
      return true;
    }

    // [spacebar] should trigger button press, leave it alone
    if ((isNodeName(target, 'button') ||
         isNodeName(target, 'input') && buttonTypes.test(target.type)) &&
        event.keyCode === key.spacebar) {
      return true;
    }

    // [arrwow keys] on radio buttons should be left alone
    if (isNodeName(target, 'input') && target.type == 'radio' &&
        arrowKeys[event.keyCode])  {
      return true;
    }

    var shift, x = 0, y = 0;
    var overflowing = overflowingAncestor(activeElement);

    if (!overflowing) {
        // Chrome iframes seem to eat key events, which we need to
        // propagate up, if the iframe has nothing overflowing to scroll
        return (isFrame && isChrome) ? parent.keydown(event) : true;
    }

    var clientHeight = overflowing.clientHeight;

    if (overflowing == document.body) {
        clientHeight = window.innerHeight;
    }

    switch (event.keyCode) {
        case key.up:
            y = -options.arrowScroll;
            break;
        case key.down:
            y = options.arrowScroll;
            break;
        case key.spacebar: // (+ shift)
            shift = event.shiftKey ? 1 : -1;
            y = -shift * clientHeight * 0.9;
            break;
        case key.pageup:
            y = -clientHeight * 0.9;
            break;
        case key.pagedown:
            y = clientHeight * 0.9;
            break;
        case key.home:
            y = -overflowing.scrollTop;
            break;
        case key.end:
            var scroll = overflowing.scrollHeight - overflowing.scrollTop;
            var scrollRemaining = scroll - clientHeight;
            y = (scrollRemaining > 0) ? scrollRemaining + 10 : 0;
            break;
        case key.left:
            x = -options.arrowScroll;
            break;
        case key.right:
            x = options.arrowScroll;
            break;
        default:
            return true; // a key we don't care about
    }

    scrollArray(overflowing, x, y);
    event.preventDefault();
    scheduleClearCache();
}