Merge pull request #18 from surjithctly/sticky-header

feat: add sticky header utility

README.md

@@ -3,6 +3,7 @@
 Astro-Navbar is a fully responsive and accessible headless navigation bar for Astro, supporting nested dropdowns and mobile-responsive toggles.
 
 ### Live Demos
+
 - [**Stackblitz**](https://stackblitz.com/edit/github-jpfnv9?file=src/pages/index.astro)
 - [**Astroship Template**](https://astroship.web3templates.com/)
 
@@ -23,6 +24,7 @@ Ensure you have the `.hidden` class in your CSS. If not, add the following:
   display: none;
 }
 ```
+
 Then integrate the navigation bar:
 
 ```astro
@@ -73,6 +75,7 @@ import { Astronav, MenuItems, MenuIcon, Dropdown, DropdownItems, DropdownSubmenu
   </Astronav>
 </div>
 ```
+
 ## Customization
 
 ### Styling
@@ -127,7 +130,7 @@ import { Astronav, MenuIcon, OpenIcon, CloseIcon } from "astro-navbar";
 
 ## Using with Tailwind CSS
 
-Astro-Navbar pairs well with Tailwind CSS. 
+Astro-Navbar pairs well with Tailwind CSS.
 
 <details>
 <summary>Minimal Usage Example with Tailwind CSS</summary>
@@ -185,6 +188,35 @@ import { Astronav, MenuItems, MenuIcon,  Dropdown, DropdownItems } from "astro-n
 
 </details>
 
+## Utilities
+
+Some related utilities are provided for convenience.
+
+### Sticky Header
+
+To make the header sticky, you can use the `<StickyHeader />` component. This will help you to add custom classes to the header when scrolled such as `sticky`. Since this is a headless component, no sticky classes has been added by default. You can add your own classes. This utility adds a tiny JS snippet to detect scroll position in a performant way.
+
+Here's an example:
+
+```js
+// Wrap the header with sticky header (renders as <header>...</header>)
+
+<StickyHeader
+  // default class. applied all the time. No changes
+  class="sticky top-0 border-b z-20 transition-all"
+  // scroll threshold to enable active class
+  scrollY={50}
+  // initial classes which will be removed when scrollY reached
+  defaultClass="py-5 border-transparent"
+  // active classes to add when scrollY reached.
+  //  "is-active" class will be added by default
+  activeClass="py-2 bg-white/80 border-gray-200 backdrop-blur-lg">
+  // ...
+  <Astronav>...</Astronav>
+  // ...
+</StickyHeader>
+```
+
 ## Options
 
 Here are the supported options / props for this plugin.

index.ts

@@ -6,3 +6,4 @@ export { default as MenuItems } from "./src/components/MenuItems.astro";
 export { default as Dropdown } from "./src/components/Dropdown.astro";
 export { default as DropdownSubmenu } from "./src/components/DropdownSubmenu.astro";
 export { default as DropdownItems } from "./src/components/DropdownItems.astro";
+export { default as StickyHeader } from "./src/components/StickyHeader.astro";

package.json

@@ -1,6 +1,6 @@
 {
   "name": "astro-navbar",
-  "version": "2.2.1",
+  "version": "2.3.0",
   "description": "Responsive Mobile Navigation with Dropdown in Astro",
   "type": "module",
   "exports": "./index.ts",

src/components/StickyHeader.astro

@@ -0,0 +1,58 @@
+---
+interface Props {
+  scrollY?: number;
+  activeClass?: string;
+  defaultClass?: string;
+  class?: string;
+}
+const {
+  scrollY = 100,
+  defaultClass = "",
+  activeClass = "",
+  class: className = "",
+} = Astro.props;
+---
+
+<header class:list={["astronav-sticky-header", className, defaultClass]}>
+  <slot />
+</header>
+
+<script define:vars={{ scrollY, defaultClass, activeClass }}>
+let scrollPos = 0;
+let ticking = false;
+
+function OnScroll(scrollPos) {
+  const headers = document.querySelectorAll(".astronav-sticky-header");
+  const classArray = activeClass.split(" ");
+  const replaceArray = defaultClass.split(" ");
+
+  headers.forEach((header) => {
+    if (scrollPos > scrollY) {
+      header.classList.remove(...replaceArray);
+      header.classList.add("is-active", ...classArray);
+      header.setAttribute("active", "");
+    }
+    //reduce the scrollY to avoid flickering when scrolling up
+    if (scrollPos < Math.max(scrollY - 20, 0)) {
+      header.classList.remove("is-active", ...classArray);
+      header.classList.add(...replaceArray);
+      header.removeAttribute("active");
+    }
+  });
+}
+
+// Scroll event throttling as per MDN
+// https://developer.mozilla.org/en-US/docs/Web/API/Document/scroll_event
+
+document.addEventListener("scroll", (event) => {
+  scrollPos = window.scrollY;
+  if (!ticking) {
+    window.requestAnimationFrame(() => {
+      OnScroll(scrollPos);
+      ticking = false;
+    });
+
+    ticking = true;
+  }
+});
+</script>