* optimize submenu in dropdown with js.

src/js/dropdown.submenu.js

++function($) {
+    $(document).on('mouseenter.zui.dropdown', '.dropdown-submenu', function() {
+        var $menu = $(this).children('.dropdown-menu');
+        var isDropUp = $menu.closest('.dropup ').length;
+        $menu.css(isDropUp ? 'bottom' : 'top', 0);
+        ($.zui.asap || setTimout)(function() {
+            var bouding = $menu[0].getBoundingClientRect();
+            if(isDropUp) {
+                $menu.css('bottom', bouding.top < 0 ? bouding.top : 0);
+            } else {
+                var bottomSpace = $(window).height() - bouding.bottom;
+                $menu.css('top', bottomSpace < 0 ? bottomSpace : 0);
+            }
+        }, 0);
+    });
+}(window.jQuery);

zui.json

@@ -937,7 +937,7 @@
       "name": "下拉菜单",
       "src": {
         "less": ["~/modules/dropdowns.less"],
-        "js": ["src/js/dropdown.js"]
+        "js": ["src/js/dropdown.js", "src/js/dropdown.submenu.js"]
       },
       "ver": "1.0.0",
       "source": "Bootstrap",