Control z-index in Fabric.js

Question

In fabricjs, I want to create a scene in which the object under the mouse rises to the top of the scene in z-index, then once the mouse leaves that object, it goes back to the z

Answer 1

Since fabric.js version 1.1.4 a new method for zIndex manipulation is available:

canvas.moveTo(object, index);
object.moveTo(index);

I think this is helpful for your use case. I've updated your jsfiddle - i hope this is what you want:
jsfiddle