Sticky

sticky.js

// Sticky
(function (el, topOffset) {
    var $el = $(el).eq(0),
        width = $el.outerWidth(),
        coords = $el.offset(),
        isSticky = false;

    topOffset = topOffset || 0;

    function relative() {
        $el.attr('style', '');
        isSticky = false;
    }

    function sticky() {
        $el.css({
            position: 'fixed',
            top: topOffset,
            left: coords.left,
            width: width
        });
        isSticky = true;
    }

    function reset() {
        width = $el.outerWidth();
        coords = $el.offset();
    }

    function defineSticky() {
        var pageYOffset = window.pageYOffset;
        if ((pageYOffset > coords.top - topOffset) && !isSticky) {
            sticky();
        } else if ((pageYOffset < coords.top - topOffset) && isSticky) {
            relative();
        }
    }

    function resizeHandler() {
        relative();
        reset();
        defineSticky();
    }

    $(window).on('scroll', defineSticky);
    $(window).on('resize', resizeHandler);

}($('.b-payment-form__info'), 20));