sticky-menu.js

// Source: https://gist.github.com/Smartik89/c6b096d82956c777079ba04a3d14d12d/
function smk_menu_sticky( _menu, _sticky_class, _container, _top ){
	_container = _container || window;
	_sticky_class = _sticky_class || 'sticky-menu';
	_menu = _menu || '.main-menu';
	_top = _top || 300;

	$( _container ).scroll(function () {
		if ($(this).scrollTop() > _top) {
			$( _menu ).addClass( _sticky_class );
		} else {
			$( _menu ).removeClass( _sticky_class );
		}
	});
};