Merge branch 'release/4.6' of git.yoho.cn:fe/yohobuywap-node into release/4.6

 var $ = require('yoho-jquery'),
     IScroll = require('yoho-iscroll');
 
-//var WILL_BEGIN = '即将开始';
+// var WILL_BEGIN = '即将开始';
 var WILL_END = '即将结束';
 var ONLINE_FORECAST = '上线预告';
 
@@ -92,8 +92,29 @@ function activeNav() {
 
 }
 
+function fixNav() {
+    var navHeight = 0;
+    var $navContainer = $('#index_nav');
+
+    if ($navContainer.size() > 0) {
+        navHeight = $navContainer.height();
+
+        // 顶部app下载位置
+        $(window).on('scroll', function() {
+            var scrollTop = $(window).scrollTop();
+
+            if (scrollTop >= navHeight) {
+                $navContainer.addClass('nav-fix');
+            } else {
+                $navContainer.removeClass('nav-fix');
+            }
+        });
+    }
+}
 
 activeNav();
+fixNav();
+
 
 module.exports = initNavScroll;
 

@@ -6,6 +6,7 @@
     white-space: nowrap;
     position: relative;
     overflow: hidden;
+    background: #fff;
 
     ul {
         padding: 0 20px;
@@ -66,3 +67,10 @@
         }
     }
 }
+
+.nav-fix {
+    position: fixed;
+    top: 0;
+    left: 0;
+    z-index: 100;
+}