[SOLVED] Slow in the middle easing function

Is there a easing function that animates slower in the middle, and faster at the beginning and end?

The easing functions I've seen so far are: ease, ease-in, ease-out, ease-in-out.

ease seems pretty similar to ease-in-out, which slows the animation at the beginning and end. I kind of want the opposite of that.

I'm creating a javascript animation to animate properties that can't be animated by CSS, such as linear-gradient.

There isn't a standard predefined one like what you're describing. But you can create a custom animation with a custom 'cubic-bezier' ease.

The alternative is to bring in a custom easing library