Scrolltrigger: Any way to return the index of a snap array on start?

[hunterruth]

Hello! 

Long story short, I'm having difficulty getting a complicated animation work directly with snapTo: labelsDirectional. I don't want the animation to scrub, but I want it to play to certain labels in the animation based on the snap point. I understand how to do this, but cannot figure out how to return the index of a current snap before it finishes. 

I have my snaps working using an object. 

 

 let snaps = [];

    panels.forEach((panel, i) => {
        snaps.push(i / panels.length);
    });

    console.log(snaps);
    

    ScrollTrigger.create({
        trigger: hero,
        pin: hero,
        start: "top top",
        end: "+=" + (panels.length * 1000),
        markers: true,
        snap: {
            snapTo: snaps,
            duration: {min: 1.5, max: 2.5},
            ease: "power2.inOut",
            onStart: (e, i) => {
                console.log(e);
            }
        }
    });

The docs don't seem to include any properties inside of the onStart function. Is it possible to return the destination snap inside onStart? Even just the decimal value would work, as I can filter the array and find the correct index. I would then use this to animate the timeline to that corresponding label. 

Thanks in advance for any nudge in the right direction! 
 

[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 CodeSandbox 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. 

[GreenSock]

Yeah, a minimal demo would be a huge help, but I did want to mention a few things: 

1. You can use getTween() to get the snapping tween (after snapping begins of course) and inspect that for data you might need.
2. If you define snapTo as a function, it'll pass you the raw value and then you can run your own logic to do the snapping (and return that value of course). It's not ideal because you don't get the benefit of leveraging ScrollTrigger's built-in labelsDirectional logic but that could be done externally with some elbow grease  But my point here is that if you're calculating it, that means you have access to the resulting value. 
3. Don't forget there's a ScrollTrigger.snapDirectional() method you could tap into for some raw logic.