tl;dr: A small-but-mighty vanilla Javascript library for interpolating an element's style based on the user's scroll.
See the fuller, flashier explanation at tween-titan.app.
If you're using React, we've also built a library called react-tween-titan.
Tween-titan can be imported as a module:
import { TweenSelf, TweenWaypoints } from 'tween-titan';
Or it can be used on an HTML page as a script.
<script src="http://unpkg.com/tween-titan"></script>
<script type="text/javascript">
const { TweenSelf, TweenWaypoints } = TweenTitan;
...
</script>
Tweens an element based on its own vertical position in the user's viewport.
Returns a Tween object.
target(HTMLElement) (required): The thing you want to tweenmargin(Object):top(number): Add (or subtract) pixels to the top of the scrollable viewport.bottom(number): Add (or subtract) pixels to the bottom of the scrollable viewport.
waypoints(Array ofwaypointobjects):percent(number): The percentage in the scroll experience where the styles should be fully transitioned.style: (Object): A set of CSS properties in Javascript style indicating what the element should look like.
stepFunction(function(percent, style, target)): A function that executes every time the tween updates.refreshInterval(number): If set, refreshes the tween at the requested interval in milliseconds. (This is useful if you're expecting layout changes on the page that could shift the tween.) Defaults to null.
Tweens an element based on the position of separate waypoint elements relative to the viewport.
Returns a Tween object.
target(HTMLElement) (required): The thing you want to tweenmargin(number): The number of pixels above (or below) the position of each waypoint that the tween should start.waypoints(Array ofwaypointobjects) (required):elem(HTMLElement): The waypoint elementstyle: (Object): A set of CSS properties in Javascript style indicating what the element should look like.
stepFunction(function(percent, style, target)): A function that executes every time the tween updates.refreshInterval(number): If set, refreshes the tween at the requested interval in milliseconds. (This is useful if you're expecting layout changes on the page that could shift the tween.) Defaults to null.
Tween.destroy(): Removes all listeners associated with a tween.Tween.refresh(): Manually paints the tween in the proper state depending on user scroll position.
As you scroll down the page, a red square spins. (Codepen)
<html>
<style type='text/css'>
.runway {
height: 150vh;
}
.square {
margin-top: 100vh;
width: 50px;
height: 50px;
background-color: red;
}
</style>
<body>
<div class='runway'>
<div class='square'></div>
</div>
</body>
<script src="http://unpkg.com/tween-titan"></script>
<script type="text/javascript">
const { TweenSelf } = TweenTitan;
const target = document.querySelector('.square');
const tween = TweenSelf.create({
target,
waypoints: [
{
percent: 0,
style: { transform: 'rotate(0deg)' }
},
{
percent: 1,
style: { transform: 'rotate(360deg)' }
}
],
});
</script>
</html>
The red square, now stuck in the center of your screen, spins in different directions depending on which waypoint you've run through. (Codepen)
<html>
<style type='text/css'>
.runway {
height: 300vh;
}
.waypoint {
margin-top: 100vh;
width: 100%;
border-top: 1px dashed black;
}
.square {
width: 50px;
height: 50px;
position: fixed;
top: calc(50vh - 25px);
left: calc(50vw - 25px);
background: red;
}
</style>
<body>
<div class='runway'>
<div class='square'></div>
<div class='waypoint' id='waypoint-1'></div>
<div class='waypoint' id='waypoint-2'></div>
<div class='waypoint' id='waypoint-3'></div>
</div>
</body>
<script src="http://unpkg.com/tween-titan"></script>
<script type="text/javascript">
const { TweenWaypoints } = TweenTitan;
const target = document.querySelector('.square');
const waypoint1 = document.querySelector('#waypoint-1');
const waypoint2 = document.querySelector('#waypoint-2');
const waypoint3 = document.querySelector('#waypoint-3');
const tween = TweenWaypoints.create({
target,
waypoints: [
{
elem: waypoint1,
style: { transform: 'rotate(0deg)' }
},
{
elem: waypoint2,
style: { transform: 'rotate(360deg)' }
},
{
elem: waypoint3,
style: { transform: 'rotate(0deg)' }
},
],
});
</script>
</html>