From 10d782ed635a9a406297e25b05bcb879c5baa460 Mon Sep 17 00:00:00 2001
From: SebinSong <songxevin@gmail.com>
Date: Mon, 2 Sep 2024 09:20:28 +1200
Subject: [PATCH] implement waitForElement() and use it for the arrow in
 about-us

---
 src/pages/about-us.astro | 20 +++++++--------
 src/utils/helpers.js     | 53 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 11 deletions(-)

diff --git a/src/pages/about-us.astro b/src/pages/about-us.astro
index fce8661..7ff8c58 100644
--- a/src/pages/about-us.astro
+++ b/src/pages/about-us.astro
@@ -136,22 +136,20 @@ import { resolvePath } from '@/utils/helpers.js'
 </Layout>
 
 <script>
-addEventListener("DOMContentLoaded", () => {
-  setTimeout(attachEventHandlers, 100)
-
-  function attachEventHandlers () {
-    const scrollDownBtn = document.body.querySelector('#scroll-down-btn')
-
-    scrollDownBtn && scrollDownBtn.addEventListener('click', () => {
-      const scrollToEl = document.querySelector('#scroll-down-to')
-
-      scrollToEl && scrollToEl.scrollIntoView({
+import { waitForElement } from '@/utils/helpers'
+
+waitForElement(
+  ['#scroll-down-btn', '#scroll-down-to'],
+  (els: Array<any>) => {
+    const [arrowBtnEl, scrollTargetEl] = els
+    arrowBtnEl.addEventListener('click', () => {
+      scrollTargetEl.scrollIntoView({
         behavior: 'smooth',
         block: 'center'
       })
     })
   }
-})
+)
 </script>
 
 <style lang="scss">
diff --git a/src/utils/helpers.js b/src/utils/helpers.js
index 65d34a0..cbe1ea7 100644
--- a/src/utils/helpers.js
+++ b/src/utils/helpers.js
@@ -18,3 +18,56 @@ export function validateEmail (email) {
   const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/
   return emailRegex.test(email)
 }
+
+export function waitForElement(
+  selectors,
+  handler,
+  timeout = 100,
+  expiry = 5000
+) {
+  // Recursively document.querySelector('...') the passed selector(s) until,
+  //
+  // 1) They are found in DOM and returned.
+  // 2) expiry duration.
+  //
+  // NOTE: This method was created to cope with the cases where <script>..</script> in .astro files
+  //       somehow get exceuted well ahead of time before the DOM rendering is completed.
+
+  let intervalIds = {}
+  let localSelectors = []
+  let foundEls = []
+  const passToHandler = () => {
+    if (!foundEls.length) { handler(null) }
+
+    handler(Array.isArray(selectors) ? foundEls : foundEls[0])
+  }
+
+  if (Array.isArray(selectors)) {
+    localSelectors = selectors
+  } else {
+    localSelectors.push(selectors)
+  }
+
+  localSelectors.filter(Boolean)
+    .forEach((selector, index) => {
+      intervalIds[selector] = setInterval(() => {
+        const foundEl = document.querySelector(selector)
+
+        if (foundEl) {
+          clearInterval(intervalIds[selector])
+          delete intervalIds[selector]
+
+          foundEls[index] = foundEl
+          if (Object.keys(intervalIds).length === 0) {
+            passToHandler()
+          }
+        }
+      }, timeout)
+    })
+
+  setTimeout(() => {
+    Object.values(intervalIds).forEach(intervalId => {
+      clearInterval(intervalId)
+    })
+  }, expiry)
+}