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how to keep the moving element where it is at the end of the animation with scrollTrigger

amapic test
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Hello,

It is a very basic feature provided by scrollTrigger but I don't manage to make it work.

Here's what I have done : https://codesandbox.io/p/github/amapic/agap22/draft/youthful-babbage

I would like the "zoom" sentence to be not pinned anymore and thus to stay where it is at the end of the animation.

For me, my code is equivalent to this one : https://cdpn.io/pen/debug/JjBwYaE?authentication_hash=bZrQWGzJymvk where the sun stay in place at the end of the animation.

What is wrong with what I have done ?

See the Pen by (@) on CodePen

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  • Solution

If you can't replicate it without React - Perhaps the problem is that React 18 runs in "strict" mode locally by default which causes your useEffect() to get called TWICE! Very annoying. It has caused a lot of headaches for a lot of people outside the GSAP community too.

 

.from() tweens use the CURRENT value as the destination and it renders immediately the value you set in the tween, so when it's called the first time it'd work great but if you call it twice, it ends up animating from the from value (no animation). It's not a GSAP bug - it's a logic thing.

 

For example, let's say el.x is 0 and you do this: 

useEffect(() => {
  // what happens if this gets called twice?
  gsap.from(el, {x: 100})
}, []);

 

The first time makes el.x jump immediately to 100 and start animating backwards toward the current value which is 0 (so 100 --> 0). But the second time, it would jump to 100 (same) and animate back to the current value which is now 100 (100 --> 100)!  See the issue?

 

In GSAP 3.11, we introduced a new gsap.context() feature that solves all of this for you. All you need to do is wrap your code in a context call, and then return a cleanup function that reverts things: 

// typically it's best to useLayoutEffect() instead of useEffect() to have React render the initial state properly from the very start.
useLayoutEffect(() => {
  let ctx = gsap.context(() => {
    // all your GSAP animation code here
  });
  return () => ctx.revert(); // <- cleanup!
}, []);

 

One of the React team members chimed in here if you'd like more background.

 

We strongly recommend reading the React article at https://greensock.com/react

 

Happy tweening!

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