There is an abundance of both CSS and JavaScript libraries for animation libraries out there. So many, in fact, that choosing the right one for your project can seem impossible. That’s the situation I faced when I decided to build an online Solitaire game. I knew I’d need an animation library, but which was the right one to choose?

In this article, I’ll go through which considerations I made, what to look out for and present you with some of the most popular libraries available. I’ll go through some real-world examples with you to illustrate my points, and in the end, hopefully, you’ll be better equipped than me when I first had to choose an animation library.

Your mileage with this advice may vary, of course. Everything I’m sharing here is specific to a thing I wanted to build. Your project may have completely different requirements and priorities and that’s OK. I think what’s important here is getting a first-hand account of thinking like a front-end developer with a particular goal.

Speaking of which, I do consider myself a front-end developer but my background is super heavy in design. So I know code, but not to the extent of someone who is a JavaScript engineer. Just wanted to clear that up because experience can certainly impact the final decision.

Here’s the goal

Before we get into any decision-making let’s take a look at the sorts of animations I needed to make in this CSS-Tricks-ified version of the game:

Pretty sweet, right? There’s nothing exactly trivial about these animations. There’s a lot going on — sometimes simultaneously — and a lot to orchestrate. Plus, a majority of the animations are triggered by user interactions. So, that left me with a few priorities heading into my decision:

• Smooth animations: The way animations are applied can have a big impact on whether they run smoothly, or display a little choppiness.
• Performance: Adopting any library is going to add weight to a project and I wanted my game to be as lean as possible.
• Convenience: I wanted a nice, clean syntax that makes it easier to write and manage the animations. I’d even trade a little extra convenience for a small performance cost if it allows me to write better, more maintainable code. Again, this bodes well for a designer-turned-developer.
• Browser support: Of course I wanted my game to work on any modern browser using some form of progressive enhancement to prevent completely borking legacy browsers. Plus, I definitely wanted  some future-proofing.

That’s what I took with me as I went in search of the right tool for this particular job.

Choosing between CSS or JavaScript animation libraries

The first thing I considered when choosing an animation library was whether to go with a CSS or JavaScript-based library. There are lots of great CSS libraries, many of them with excellent performance which was a high priority for me. I was looking to do some heavy-duty animations, like the  ability to sequence animations and get callbacks on animation completion. That’s all totally possible with pure CSS — still, it’s a lot less smooth than what most JavaScript libraries offer.

Let’s see how a simple sequenced animation looks in CSS and compare it to jQuery, which has plenty of built-in animation helpers:

The animations look the same but are created differently. To make the CSS animation, first, we have to define the keyframe animation in our CSS and attach it to a class:

.card.move {
  animation : move 2s;
}

@keyframes move {
  0% { left: 0 }
  50% { left: 100px }
  100% { left: 0 }
}

We then execute the animation using JavaScript and listen for a CSS callback on the element:

var cardElement = document.getElementsByClassName("card")[0];
var statusElement = document.getElementsByClassName("status")[0];

cardElement.classList.add("move");
statusElement.innerHTML = "Animating"

var animationEndCallback = function() {
  cardElement.classList.remove("move");
  statusElement.innerHTML = "Inactive"
}

cardElement.addEventListener("webkitAnimationEnd", animationEndCallback);
cardElement.addEventListener("oAnimationEnd", animationEndCallback); 
cardElement.addEventListener("antionend", animationEndCallback);

Having things happen in different places might be fine in a simple example like this, but it can become very confusing once things get a bit more complex. 

Compare this to how the animation is done with jQuery:

$(".status").text("Animating")
$( ".card" ).animate({
  left: "100px"
}, 1000);
$( ".card" ).animate({
  left: 0
}, 1000, function() {
  $(".status").text("Inactive")
});

Here, everything happens in the same place, simplifying things should the animations grow more complex in the future.

It seemed clear that a JavaScript library was the right way to go, but which was the right one to choose for my Solitaire game? I mean, jQuery is great and still widely used even today, but that’s not something I want to hang my hat on. There are plenty of JavaScript animation libraries, so I wanted to consider something built specifically to handle the type of heavy animations I had in mind.

Choosing a JavaScript animation library

It quickly became apparent to me that there’s no lack of JavaScript animation libraries and new, exciting technologies. They all have benefits and drawbacks, so let’s go through some of the ones I considered and why.

The Web Animations API is one such case that might replace many JavaScript animation libraries in the future. With it, you’ll be able to create complex staggered animations without loading any external libraries and with the same performance as CSS animations. The only drawback is that not all browsers support it yet. 

The <canvas> element presents another exciting opportunity. In it, we can animate things with JavaScript, as we would with the DOM, but the animation is rendered as raster, which means we can make some high-performance animations. The only drawback is that the canvas element is essentially rendered as an image in the DOM, so if we’re looking for pixel-perfection, we might be out of luck. As someone acutely in tune with design, this was a dealbreaker for me.

I needed something tried and tested, so I knew I probably had to go with one of the many JavaScript libraries. I started looking at libraries and narrowed my choices to Anime.js and GSAP. They both seemed to handle complex animations well and had excellent notes on performance. Anime is a well-maintained library with over 42.000 stars on GitHub, while GSAP is a super popular, battle-tested library with a thriving community.

An active community was critical to me since I needed a place to ask for help, and I didn’t want to use a library that might later be abandoned. I considered this as part of my convenience requirements.

Sequencing animations and callbacks

Once I had my choices narrowed down, the next step was to implement a complex animation using my two libraries. A recurrent animation in a solitaire game is that of a card moving somewhere and then turning over, so let’s see how that looks:

Both animations look great! They’re smooth, and implementing both of them was pretty straightforward. Both libraries had a timeline function that made creating sequences a breeze. This is how the implementation looks in AnimeJS:

var timeline = anime.timeline({
  begin: function() {
    $(".status").text("Animating")
  },
  complete: function() {
    $(".status").text("Inactive")
  }
});

timeline.add({
  targets: '.card',
  left: [0, 300],
  easing: 'easeInOutSine',
  duration: 500
}).add({
  targets: '.card .back',
  rotateY: [0, 90],
  easing: 'easeInSine',
  duration: 200
}).add({
  targets: '.card .front',
  rotateY: [-90, 0],
  easing: 'easeOutSine',
  duration: 200
})

Anime’s timeline() function comes built-in with callbacks on beginning and ending the animation, and creating the sequence is as easy as appending the sequential animations. First, I move the card, then I turn my back-image 90 degrees, so it goes out of view, and then I turn my front-image 90 degrees, so it comes into view.

The same implementation using GSAP’s timeline() function looks very similar:

var timeline = gsap.timeline({
  onStart: function() {
    $(".status").text("Animating")
  },
  onComplete: function() {
    $(".status").text("Inactive")
  }
});

timeline.fromTo(".card", {
  left: 0
}, {
  duration: 0.5,
  left: 300
}).fromTo(".card .back", {
  rotationY: 0
}, {
  rotationY: 90,
  ease: "power1.easeIn",
  duration: 0.2
}).fromTo(".card .front", {
  rotationY: -90
}, {
  rotationY: 0,
  ease: "power1.easeOut",
  duration: 0.2
})

Decision time

The main difference between Anime and GSAP appears to be the syntax, where GSAP might be a little more elaborate. I was stuck with two great libraries that had very similar functionality, were able to deal with complex animation, and had a thriving community. It seemed like I had a tie race!

So, what made me choose one library over the other?

I was very concerned about how the library would act under pressure. Having laggy animations in a game like Solitaire can greatly impact how fun it is to play the game. I knew I wouldn’t be able to fully see how the library performed before I created the game. Luckily, GSAP had made a stress test that compared different animation libraries to each other, including Anime.

Looking at that, GSAP certainly looked to be the superior library for dealing with loads of complex animations. GSAP was giving me upwards of 26 frames per second on a heavy animation that Anime was only able to top out at 19.  After reading up on GSAP more and looking into their forums, it became clear that performance was of the highest priority to the guys behind GSAP.

And even though both GSAP and Anime have been around a while, Anime’s repo has been sitting somewhat dormant a couple of years while GSAP had made commits in the past couple of months.

I ended up using GSAP and haven’t regretted my decision!

How about you? Does any of this square with how you evaluate and compare front-end tooling? Are there other priorities you might have considered (e.g. accessibility, etc.) in a project like this? Or do you have a project where you had to pare down your choices from a bunch of different options? Please share in the comments because I’d like to know! 

Oh, and if you want to see how it looks when animating a whole deck of cards, you can head over to my site and play a game of Solitaire. Have fun!