function trapFocus(element) {
    var focusableEls = element.querySelectorAll('a[href]:not([disabled]), button:not([disabled]), textarea:not([disabled]), input[type="text"]:not([disabled]), input[type="radio"]:not([disabled]), input[type="checkbox"]:not([disabled]), select:not([disabled]), input[type="submit"]:not([disabled]), iframe'),
        firstFocusableEl = focusableEls[0],
        lastFocusableEl = focusableEls[focusableEls.length - 1],
        KEYCODE_TAB = 9;