smooth scroll for hash anchors

lib/app/composables/router.js

@@ -3,8 +3,9 @@ import { reactive, provide } from 'vue'
 export const RouteSymbol = Symbol()
 
 export function useRouter() {
+  const loc = location
   const route = reactive({
-    path: location.pathname,
+    path: loc.pathname,
     scrollPosition: window.scrollY
   })
 
@@ -16,18 +17,32 @@ export function useRouter() {
     (e) => {
       if (e.target.tagName === 'A') {
         const { href, target } = e.target
+        const url = new URL(href)
         if (
           target !== `_blank` &&
-          href.startsWith(`${location.protocol}//${location.host}`)
+          url.protocol === loc.protocol &&
+          url.hostname === loc.hostname
         ) {
+          if (url.pathname === loc.pathname) {
+            // smooth scroll bewteen hash anchors in the same page
+            if (url.hash !== loc.hash) {
+              e.preventDefault()
+              window.scrollTo({
+                left: 0,
+                top: e.target.offsetTop,
+                behavior: 'smooth'
+              })
+            }
+          } else {
             e.preventDefault()
             // save scroll position before changing url
             saveScrollPosition()
             history.pushState(null, '', href)
-          route.path = location.pathname
+            route.path = loc.pathname
             route.scrollPosition = 0
           }
         }
+      }
     },
     { capture: true }
   )
@@ -39,7 +54,7 @@ export function useRouter() {
      */
     (e) => {
       route.path = location.pathname
-      route.scrollPosition = e.state && e.state.scrollPosition || 0
+      route.scrollPosition = (e.state && e.state.scrollPosition) || 0
     }
   )