ios-scroll-prevention.js

/**
 * keep body from scrolling when nav menu is open in iOS
 */
$(document).on('touchmove', function(e){
    if($('body').hasClass('nav-showing')){
        var $target = $(e.target);
        if($target.is('#nav-wrapper') || $target.parents('#nav-wrapper')){
            e.stopPropagation();
        }
    }
});