I'm trying to create a progress bar that shows how much of a certain element the user still has left to view. Here are some details:
.postProgressBar
appears by default under.postHeroImage
- When the user scrolls, I want the
.postProgressBar
to slowly fill up based on how much of the.spacer
element there is left to scroll to. - When the
.postProgressBar
hits the bottom of myheader
, I want it to becomefixed
to the bottom of theheader
(and to unfix when.postHeroImage
is in view again).
See my current approach:
$(function() {
gsap.registerPlugin(ScrollTrigger);
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll >= 1) {
$(".header").addClass("fixed");
} else {
$(".header").removeClass("fixed");
}
});
var action = gsap.set('.postProgressBar', { position:'fixed', paused:true});
gsap.to('progress', {
value: 100,
ease: 'none',
scrollTrigger: {
trigger: "#startProgressBar",
scrub: 0.3,
markers:true,
onEnter: () => action.play(),
onLeave: () => action.reverse(),
onLeaveBack: () => action.reverse(),
onEnterBack: () => action.reverse(),
}
});
});
body {
background-color: lightblue;
--white: #FFFFFF;
--grey: #002A54;
--purple: #5D209F;
}
.header {
position: absolute;
top: 0;
width: 100%;
padding: 20px 15px;
z-index: 9999;
background-color: var(--white);
}
.header.fixed {
position: fixed;
background-color: var(--white);
border-bottom: 1px solid var(--grey);
}
.postHeroImage {
padding: 134px 0 0 0;
margin-bottom: 105px;
position: relative;
}
.postHeroImage__bg {
background-size: cover;
background-repeat: no-repeat;
width: 100%;
min-height: 400px;
}
progress {
position: absolute;
bottom: -15px;
left: 0;
-webkit-appearance: none;
appearance: none;
width: 100%;
height: 15px;
border: none;
background: transparent;
z-index: 9999;
}
progress::-webkit-progress-bar {
background: transparent;
}
progress::-webkit-progress-value {
background: var(--purple);
background-attachment: fixed;
}
progress::-moz-progress-bar {
background: var(--purple);
background-attachment: fixed;
}
.spacer {
height: 1000vh;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/gsap/3.9.0/gsap.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/gsap/3.9.0/ScrollTrigger.min.js"></script>
<link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet">
<body>
<header >Header</header>
<section id="startProgressBar">
<progress max="100" value="0"></progress>
<div >
<div >
<div >
<div style="background-image: url( 'https://picsum.photos/200/300' );" loading="lazy"></div>
</div>
</div>
</div>
</section>
<div >lorum ipsum</div>
</body>
Current issues:
- The
.postProgressBar
doesn't becomefixed
(can't seefixed
inline style in inspect mode) - The
.postProgressBar
is showing progress that isn't accurate based on the amount of.spacer
there is left to scroll.
CodePudding user response:
Instead of the library that you use, you could simply use the HTML tag <progress>
(your library is using the same).
Here is a simple way of how you can do it:
const scrollHeight = Math.max(
document.body.scrollHeight, document.documentElement.scrollHeight,
document.body.offsetHeight, document.documentElement.offsetHeight,
document.body.clientHeight, document.documentElement.clientHeight
);
window.addEventListener('scroll', (e) => document.querySelector('progress').value = window.pageYOffset / (scrollHeight - window.innerHeight) * 100)
html, body {
padding: 0;
margin: 0;
height: 2500px;
}
progress {
position: fixed;
border-radius: 0;
width: 100%;
height: 22px;
}
progress::-webkit-progress-value {
background-color: #5D209F;
}
<progress value="0" max="100"></progress>
Every time the user scrolls the page, the progress gets a value, which is current height position / (document's height - active screen height) * 100.
CodePudding user response:
- Position sticky is very useful here. You can use it for header as well as for the progress bar. With no effort it'll keep the elements fixed to top.
- For accurate position you need to use
start
andend
properties of thescrollTrigger
. This will tell the gsap when to start animating and when to end. For end we need to add 64px, the height of the header, to the scrolling cos our container is 64px below from top of the viewport.
Demo:
$(function() {
//read the css variable
let bodyStyles = window.getComputedStyle(document.body);
let headerHeight = bodyStyles.getPropertyValue('--header-height');
gsap.registerPlugin(ScrollTrigger);
gsap.to('progress', {
value: 100,
ease: 'none',
scrollTrigger: {
trigger: "#startProgressBar",
scrub: 0.3,
start: 'start 0px',
end: 'bottom' headerHeight,
markers: true,
}
});
});
body {
background-color: lightblue;
--white: wheat;
--grey: #002A54;
--purple: #5D209F;
/* 40px padding top and bottom 24px line height*/
--header-height: 64px;
}
.header {
/* position: absolute;*/
position: sticky;
top: 0;
width: 100%;
padding: 20px 15px;
z-index: 9999;
background-color: var(--white);
}
.postHeroImage {
padding: 134px 0 0 0;
margin-bottom: 105px;
position: relative;
}
.postHeroImage__bg {
background-size: cover;
background-repeat: no-repeat;
width: 100%;
min-height: 400px;
}
progress {
position: sticky;
top: var(--header-height);
left: 0;
-webkit-appearance: none;
appearance: none;
width: 100%;
height: 15px;
border: none;
background: transparent;
/*z-index: 9999;*/
}
progress::-webkit-progress-bar {
background: transparent;
}
progress::-webkit-progress-value {
background: var(--purple);
background-attachment: fixed;
}
progress::-moz-progress-bar {
background: var(--purple);
background-attachment: fixed;
}
.spacer {
height: 1000vh;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/gsap/3.9.0/gsap.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/gsap/3.9.0/ScrollTrigger.min.js"></script>
<link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet">
<header >Header</header>
<section id="startProgressBar">
<progress max="100" value="0"></progress>
<div >
<div >
<div >
<div style="background-image: url( 'https://picsum.photos/id/705/300/200' );" loading="lazy"></div>
</div>
</div>
</div>
</section>
<div >lorum ipsum</div>
You can play with start and end properties. If you want to track progress on the content only then change
trigger
to '.container'
.