gistfile1.js

// умное позиционирование
var win = $(window);
var topOffset = selectbox.offset().top;
var bottomOffset = win.height() - selectHeight - (topOffset - win.scrollTop());
var visible = opt.selectVisibleOptions;
var  minHeight = liHeight * 6;
var	newHeight = liHeight * visible;
if (visible > 0 && visible < 6) minHeight =  newHeight;
// раскрытие вверх
if (bottomOffset < 0 || bottomOffset < minHeight)	{
	dropdown.height('auto').css({top: 'auto', bottom: position});
	if (dropdown.outerHeight() > topOffset - win.scrollTop() - 20 ) {
		dropdown.height(Math.floor((topOffset - win.scrollTop() - 20) / liHeight) * liHeight);
		if (visible > 0 && visible < 6) {
			if (dropdown.height() > minHeight) dropdown.height(minHeight);
		} else if (visible > 6) {
			if (dropdown.height() > newHeight) dropdown.height(newHeight);
		}
	}
// раскрытие вниз
} else if (bottomOffset > minHeight) {
	dropdown.height('auto').css({bottom: 'auto', top: position});
	if (dropdown.outerHeight() > bottomOffset - 20 ) {
		dropdown.height(Math.floor((bottomOffset - 20) / liHeight) * liHeight);
		if (visible > 0 && visible < 6) {
			if (dropdown.height() > minHeight) dropdown.height(minHeight);
		} else if (visible > 6) {
			if (dropdown.height() > newHeight) dropdown.height(newHeight);
		}
	}
}