Created
July 3, 2020 17:41
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Sticky scroll spy example
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<!DOCTYPE html> | |
<html lang="en"> | |
<head> | |
<meta charset="UTF-8"> | |
<meta name="viewport" content="width=device-width, initial-scale=1.0"> | |
<title>Sticky scroll spy example</title> | |
<style> | |
html { | |
scroll-behavior: smooth; | |
} | |
.section-nav li.active>a { | |
color: #333; | |
font-weight: 500; | |
} | |
.section-nav { | |
padding-left: 0; | |
} | |
.section-nav a { | |
text-decoration: none; | |
display: block; | |
padding: .125rem 0; | |
color: #ccc; | |
transition: color 50ms ease-in-out; | |
} | |
.section-nav a:hover, | |
.section-nav a:focus { | |
color: #666; | |
} | |
/** Poor man's reset **/ | |
* { | |
box-sizing: border-box; | |
} | |
html, | |
body { | |
background: #fff; | |
margin: 0; | |
padding: 0; | |
} | |
body { | |
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif; | |
} | |
ul, | |
ol { | |
list-style: none; | |
margin: 0; | |
padding: 0; | |
} | |
li { | |
display: inline-block; | |
margin-left: 1rem; | |
} | |
h1 { | |
font-weight: 300; | |
} | |
h2 { | |
padding-top: 1rem; | |
} | |
/** page layout **/ | |
main { | |
max-width: 100em; | |
width: 90%; | |
margin: 0 auto; | |
} | |
section { | |
height: 50rem; | |
margin-bottom: calc(5rem + 1px); | |
scroll-margin-top: 5rem; | |
} | |
.sticky-nav { | |
position: sticky; | |
top: 0; | |
background-color: antiquewhite; | |
padding: 2rem; | |
} | |
</style> | |
</head> | |
<body> | |
<main> | |
<h1>Lorem ipsum dolor sit amet consectetur adipisicing elit. Excepturi, voluptatem labore vitae temporibus porro | |
odit dicta libero soluta officia quae, officiis ipsa impedit in eveniet maiores similique enim doloribus | |
voluptates!</h1> | |
<nav class="section-nav sticky-nav"> | |
<ol> | |
<li><a href="#section1">Section 1</a></li> | |
<li><a href="#section2">Section 2</a></li> | |
<li><a href="#section3">Section 3</a></li> | |
<li><a href="#section4">Section 4</a></li> | |
<li><a href="#section5">Section 5</a></li> | |
</ol> | |
</nav> | |
<section id="section1"> | |
<h2>Section 1</h2> | |
<p>…</p> | |
</section> | |
<section id="section2"> | |
<h2>Section 2</h2> | |
<p>…</p> | |
</section> | |
<section id="section3"> | |
<h2>Section 3</h2> | |
<p>…</p> | |
</section> | |
<section id="section4"> | |
<h2>Section 4</h2> | |
<p>…</p> | |
</section> | |
<section id="section5"> | |
<h2>Section 5</h2> | |
<p>…</p> | |
</section> | |
</main> | |
<script> | |
window.addEventListener('DOMContentLoaded', () => { | |
const stickyHeight = document.querySelector('.sticky-nav').getBoundingClientRect().height; | |
const viewportHeight = window.innerHeight | |
const bottomMargin = viewportHeight - stickyHeight | |
let options = { | |
rootMargin: `0px 0px -${bottomMargin}px 0px`, | |
} | |
function updateActiveNav(entries) { | |
requestIdleCallback(() => { | |
entries.forEach(entry => { | |
const id = entry.target.getAttribute('id'); | |
if (entry.isIntersecting) { | |
if (!document.querySelector(`nav li a[href="#${id}"]`)) { | |
return | |
} | |
document.querySelector(`nav li a[href="#${id}"]`).parentElement.classList.add('active'); | |
} else { | |
if (!document.querySelector(`nav li a[href="#${id}"]`)) { | |
return | |
} | |
document.querySelector(`nav li a[href="#${id}"]`).parentElement.classList.remove('active'); | |
} | |
}); | |
}) | |
} | |
const observer = new IntersectionObserver(updateActiveNav, options); | |
document.querySelectorAll('section[id]').forEach((section) => { | |
observer.observe(section); | |
}); | |
}); | |
</script> | |
</body> | |
</html> |
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