Animation issues when using IntersectionObserver

[Pavel123]

Hello Everyone, help me understand what the problem is. When I am at the beginning of the page, my animation works without errors, but if I reload the page while in the middle or at the end of an animation block that uses IntersectionObserver, I get this error.

[GSAP Helper]

It's pretty tough to troubleshoot without a minimal demo - the issue could be caused by CSS, markup, a third party library, your browser, an external script that's totally unrelated to GSAP, etc. Would you please provide a very simple CodePen or Stackblitz that demonstrates the issue? 

 

Please don't include your whole project. Just some colored <div> elements and the GSAP code is best (avoid frameworks if possible). See if you can recreate the issue with as few dependancies as possible. If not, incrementally add code bit by bit until it breaks. Usually people solve their own issues during this process! If not, then at least we have a reduced test case which greatly increases your chances of getting a relevant answer.

 

Here's a starter CodePen that loads all the plugins. Just click "fork" at the bottom right and make your minimal demo: 

See the Pen aYYOdN by GreenSock (@GreenSock) on CodePen

 

If you're using something like React/Next/Vue/Nuxt or some other framework, you may find StackBlitz easier to use. We have a series of collections with different templates for you to get started on these different frameworks: React/Next/Vue/Nuxt.

 

Once we see an isolated demo, we'll do our best to jump in and help with your GSAP-specific questions. 

[Pavel123]

See the Pen yLQRbPW by wthddymb-the-bashful (@wthddymb-the-bashful) on CodePen

[Pavel123]

Поскольку в реальном проекте, когда мы перезагружаем страницу, мы остаемся в области перезагрузки, вам нужно будет быстро прокрутить вниз в CodePen, чтобы воспроизвести эту проблему.

15 minutes ago, Pavel123 said:

 

 

 

[Rodrigo]

Hi,

 

I have zero experience with Intersection Observer so I couldn't tell you exactly what the problem is, but clearly is related to that because if I just create the stagger animation for the elements without it I don't get the error.

 

I think in this case ScrollTrigger Batch would be the best way to solve your issue. Besides working on top of ScrollTrigger, ScrollTrigger is far more optimized than Intersection Observer:

https://greensock.com/docs/v3/Plugins/ScrollTrigger/static.batch()

 

Here is a simple example of how it works:

See the Pen NWGPxGZ by GreenSock (@GreenSock) on CodePen

 

Here is a more complete example:

See the Pen zYrxpmb by GreenSock (@GreenSock) on CodePen

 

Hopefully this helps.

Happy Tweening!

[Pavel123]

Thank you very much for your feedback and the provided example.

[GreenSock]

Just to clarify the issue, it had nothing to do with ScrollTrigger/GSAP or IntersectionObserver - the problem had to do with the fact that you were creating a targets Array that had empty slots, sorta like: 

let targets = [undefined, undefined, undefined, div, div];

gsap.fromTo(targets, {...}, {...});

Because of the way you were doing your map(). 

 

I assume you meant to do something more like this:

var cardElements = document.querySelectorAll('.card');
var observer = new IntersectionObserver(function(observerEntries, self) {
  var targets = [];
  observerEntries.forEach(function (entry) {
    if (entry.isIntersecting) {
      self.unobserve(entry.target);
      targets.push(entry.target);
    }
  });
  gsap.fromTo(
    targets, 
    {x: '25%', opacity: 0,},
    {x: 0,
     opacity: 1,
     stagger: 0.3,
     duration: .7,
     delay: 0.3,},
  );
});
cardElements.forEach(function (element) {
  observer.observe(element);
});

But like Rodrigo said, ScrollTrigger.batch() is probably better/cleaner.