Animation Crossfade?

Do we have a method for crossfading animations?
In Three.js for example on an animation you can do animation.action.crossFadeFrom(otherAnimation.action, 0.5, true)

To smoothly blend a transition between animations.

Or am I going to need to make a function that checks the current weight of the animation and then lerps the both weights of the animations in relation to that?

Is this what you need?

Skeleton animations sorry should have clarified.

DK made I nice video that might be helpful:

Haha yeah, I understand all those concepts. I know how to do what I need just making sure that there is not a method to do it already.

Just trying to wire up my animation finite state machine to have smooth transitions without having to script something for it.