$(document).ready(function(){
    $('#main-nav li').mouseenter(function(){
        if($(window).height() < 635){
            var currentHeight = $(window).height() - 100;
            var intConvert = currentHeight.toString();
            var heightString = intConvert.concat('px');

            $('#main-nav .sub-menu').each(function(){
                $(this).css('max-height', heightString);
            });
        }
    });

    $(window).on('resize', function(){
        if($(window).height() >= 635){
            $('#main-nav .sub-menu').each(function(){
                $(this).css('max-height', 'none');
            });
        }
    });
});