fix: fix sidebar active status not working as expected (#140) (#149)

src/client/theme-default/composables/activeSidebarLink.ts

@@ -3,19 +3,42 @@ import { onMounted, onUnmounted, onUpdated } from 'vue'
 export function useActiveSidebarLinks() {
   let rootActiveLink: HTMLAnchorElement | null = null
   let activeLink: HTMLAnchorElement | null = null
-  const decode = decodeURIComponent
 
-  const deactiveLink = (link: HTMLAnchorElement | null) =>
-    link && link.classList.remove('active')
+  const onScroll = throttleAndDebounce(setActiveLink, 300)
+
+  function setActiveLink(): void {
+    const sidebarLinks = getSidebarLinks()
+    const anchors = getAnchors(sidebarLinks)
 
-  const activateLink = (hash: string) => {
+    for (let i = 0; i < anchors.length; i++) {
+      const anchor = anchors[i]
+      const nextAnchor = anchors[i + 1]
+
+      const [isActive, hash] = isAnchorActive(i, anchor, nextAnchor)
+
+      if (isActive) {
+        history.replaceState(null, document.title, hash ? hash : ' ')
+        activateLink(hash)
+        return
+      }
+    }
+  }
+
+  function activateLink(hash: string | null): void {
     deactiveLink(activeLink)
     deactiveLink(rootActiveLink)
+
     activeLink = document.querySelector(`.sidebar a[href="${hash}"]`)
-    if (activeLink) {
+
+    if (!activeLink) {
+      return
+    }
+
     activeLink.classList.add('active')
+
     // also add active class to parent h2 anchors
-      const rootLi = activeLink.closest('.sidebar > ul > li')
+    const rootLi = activeLink.closest('.sidebar-links > ul > li')
+
     if (rootLi && rootLi !== activeLink.parentElement) {
       rootActiveLink = rootLi.querySelector('a')
       rootActiveLink && rootActiveLink.classList.add('active')
@@ -23,66 +46,81 @@ export function useActiveSidebarLinks() {
       rootActiveLink = null
     }
   }
+
+  function deactiveLink(link: HTMLAnchorElement | null): void {
+    link && link.classList.remove('active')
   }
 
-  const setActiveLink = () => {
-    const sidebarLinks = [].slice.call(
-      document.querySelectorAll('.sidebar a')
-    ) as HTMLAnchorElement[]
+  onMounted(() => {
+    setActiveLink()
+    window.addEventListener('scroll', onScroll)
+  })
+
+  onUpdated(() => {
+    // sidebar update means a route change
+    activateLink(decodeURIComponent(location.hash))
+  })
 
-    const anchors = [].slice
+  onUnmounted(() => {
+    window.removeEventListener('scroll', onScroll)
+  })
+}
+
+function getSidebarLinks(): HTMLAnchorElement[] {
+  return [].slice.call(
+    document.querySelectorAll('.sidebar a.sidebar-link-item')
+  )
+}
+
+function getAnchors(sidebarLinks: HTMLAnchorElement[]): HTMLAnchorElement[] {
+  return [].slice
     .call(document.querySelectorAll('.header-anchor'))
     .filter((anchor: HTMLAnchorElement) =>
       sidebarLinks.some((sidebarLink) => sidebarLink.hash === anchor.hash)
     ) as HTMLAnchorElement[]
+}
 
-    const pageOffset = (document.querySelector('.navbar') as HTMLElement)
-      .offsetHeight
-    const scrollTop = window.scrollY
+function getPageOffset(): number {
+  return (document.querySelector('.navbar') as HTMLElement).offsetHeight
+}
 
-    const getAnchorTop = (anchor: HTMLAnchorElement): number =>
-      anchor.parentElement!.offsetTop - pageOffset - 15
+function getAnchorTop(anchor: HTMLAnchorElement): number {
+  const pageOffset = getPageOffset()
 
-    for (let i = 0; i < anchors.length; i++) {
-      const anchor = anchors[i]
-      const nextAnchor = anchors[i + 1]
-      const isActive =
-        (i === 0 && scrollTop === 0) ||
-        (scrollTop >= getAnchorTop(anchor) &&
-          (!nextAnchor || scrollTop < getAnchorTop(nextAnchor)))
+  return anchor.parentElement!.offsetTop - pageOffset - 15
+}
 
-      // TODO: fix case when at page bottom
+function isAnchorActive(
+  index: number,
+  anchor: HTMLAnchorElement,
+  nextAnchor: HTMLAnchorElement
+): [boolean, string | null] {
+  const scrollTop = window.scrollY
 
-      if (isActive) {
-        const targetHash = decode(anchor.hash)
-        history.replaceState(null, document.title, targetHash)
-        activateLink(targetHash)
-        return
-      }
-    }
+  if (index === 0 && scrollTop === 0) {
+    return [true, null]
   }
 
-  const onScroll = throttleAndDebounce(setActiveLink, 300)
-  onMounted(() => {
-    setActiveLink()
-    window.addEventListener('scroll', onScroll)
-  })
+  if (scrollTop < getAnchorTop(anchor)) {
+    return [false, null]
+  }
 
-  onUpdated(() => {
-    // sidebar update means a route change
-    activateLink(decode(location.hash))
-  })
+  if (!nextAnchor || scrollTop < getAnchorTop(nextAnchor)) {
+    return [true, decodeURIComponent(anchor.hash)]
+  }
 
-  onUnmounted(() => {
-    window.removeEventListener('scroll', onScroll)
-  })
+  return [false, null]
 }
 
 function throttleAndDebounce(fn: () => void, delay: number): () => void {
   let timeout: NodeJS.Timeout
   let called = false
+
   return () => {
-    if (timeout) clearTimeout(timeout)
+    if (timeout) {
+      clearTimeout(timeout)
+    }
+
     if (!called) {
       fn()
       called = true