diff --git a/src/components/layout/sider.vue b/src/components/layout/sider.vue
index 16ed865..9cae962 100644
--- a/src/components/layout/sider.vue
+++ b/src/components/layout/sider.vue
@@ -15,15 +15,8 @@
 </template>
 <script>
     import { on, off } from '../../utils/dom';
-    import { oneOf } from '../../utils/assist';
+    import { oneOf, dimensionMap } from '../../utils/assist';
     const prefixCls = 'ivu-layout-sider';
-    const dimensionMap = {
-        xs: '480px',
-        sm: '768px',
-        md: '992px',
-        lg: '1200px',
-        xl: '1600px',
-    };
     if (typeof window !== 'undefined') {
         const matchMediaPolyfill = mediaQuery => {
             return {
diff --git a/src/utils/assist.js b/src/utils/assist.js
index 227a3c5..97fcf57 100644
--- a/src/utils/assist.js
+++ b/src/utils/assist.js
@@ -278,3 +278,11 @@ export function removeClass(el, cls) {
         el.className = trim(curClass);
     }
 }
+
+export const dimensionMap = {
+    xs: '480px',
+    sm: '768px',
+    md: '992px',
+    lg: '1200px',
+    xl: '1600px',
+};
\ No newline at end of file
--
libgit2 0.21.4