docs: improve anchor scrolling

packages/vant-cli/site/desktop/main.js

@@ -1,6 +1,7 @@
 import Vue from 'vue';
 import App from './App';
 import { router } from './router';
+import { scrollToAnchor } from './utils';
 
 if (process.env.NODE_ENV !== 'production') {
   Vue.config.productionTip = false;
@@ -10,15 +11,7 @@ new Vue({
   el: '#app',
   mounted() {
     if (this.$route.hash) {
-      // wait page init
-      setTimeout(() => {
-        const el = document.querySelector(this.$route.hash);
-        if (el) {
-          el.scrollIntoView({
-            behavior: 'smooth'
-          });
-        }
-      }, 1000);
+      scrollToAnchor(this.$route.hash);
     }
   },
   render: h => h(App),

packages/vant-cli/site/desktop/utils.js

@@ -0,0 +1,19 @@
+export function scrollToAnchor(selector) {
+  let count = 0;
+
+  const timer = setInterval(() => {
+    const el = document.querySelector(selector);
+    if (el) {
+      el.scrollIntoView({
+        behavior: 'smooth'
+      });
+      clearInterval(timer);
+    } else {
+      count++;
+
+      if (count > 10) {
+        clearInterval(timer);
+      }
+    }
+  }, 100);
+}