diff --git a/build/webpack.dev.js b/build/webpack.dev.js
index 9447fe67f..df8f05ab7 100644
--- a/build/webpack.dev.js
+++ b/build/webpack.dev.js
@@ -49,6 +49,7 @@ module.exports = {
       },
       {
         test: /\.less$/,
+        sideEffects: true,
         use: [
           'style-loader',
           'css-loader',
@@ -63,10 +64,7 @@ module.exports = {
       },
       {
         test: /\.md$/,
-        use: [
-          'vue-loader',
-          '@vant/markdown-loader'
-        ]
+        use: ['vue-loader', '@vant/markdown-loader']
       },
       {
         test: /\.(ttf|svg)$/,
diff --git a/docs/src/router.js b/docs/src/router.js
index 3ae381b6e..a7e6d3cd0 100644
--- a/docs/src/router.js
+++ b/docs/src/router.js
@@ -3,7 +3,9 @@ import docConfig from './doc.config';
 import DemoList from './components/DemoList';
 import DemoPages from './components/DemoPages';
 import { demoWrapper } from './demo-common';
-import './utils/iframe-router';
+import { initIframeRouter } from './utils/iframe-router';
+
+initIframeRouter();
 
 const registerRoute = ({ mobile, componentMap }) => {
   const route = [
diff --git a/docs/src/utils/iframe-router.js b/docs/src/utils/iframe-router.js
index 8a8b23e5d..45b1f664f 100644
--- a/docs/src/utils/iframe-router.js
+++ b/docs/src/utils/iframe-router.js
@@ -5,30 +5,32 @@
 import { setLang } from './lang';
 import { iframeReady, isMobile } from '.';
 
-window.syncPath = function () {
-  const router = window.vueRouter;
-  const isInIframe = window !== window.top;
-  const currentDir = router.history.current.path;
-  const pathParts = currentDir.split('/');
-  let lang = pathParts[0];
-  if (currentDir[0] === '/') {
-    lang = pathParts[1];
-  }
-
-  if (!isInIframe && !isMobile) {
-    const iframe = document.querySelector('iframe');
-    if (iframe) {
-      iframeReady(iframe, () => {
-        iframe.contentWindow.changePath(lang, currentDir);
-      });
+export function initIframeRouter() {
+  window.syncPath = function () {
+    const router = window.vueRouter;
+    const isInIframe = window !== window.top;
+    const currentDir = router.history.current.path;
+    const pathParts = currentDir.split('/');
+    let lang = pathParts[0];
+    if (currentDir[0] === '/') {
+      lang = pathParts[1];
     }
-    setLang(lang);
-  } else if (isInIframe) {
-    window.top.changePath(lang, currentDir);
-  }
-};
 
-window.changePath = function (lang, path = '') {
-  setLang(lang);
-  window.vueRouter.replace(path);
-};
+    if (!isInIframe && !isMobile) {
+      const iframe = document.querySelector('iframe');
+      if (iframe) {
+        iframeReady(iframe, () => {
+          iframe.contentWindow.changePath(lang, currentDir);
+        });
+      }
+      setLang(lang);
+    } else if (isInIframe) {
+      window.top.changePath(lang, currentDir);
+    }
+  };
+
+  window.changePath = function (lang, path = '') {
+    setLang(lang);
+    window.vueRouter.replace(path);
+  };
+}