This extension implements several custom animations within GoJS. It may be useful to copy some of them into your own project.
Options:
GoJS offers several built-in animations, enabled by default, as well as the ability to create arbitrary animations.
The Diagram.animationManager handles animations within a Diagram. The AnimationManager automatically sets up and dispatches default animations, and has properties to customize and disable them. Custom animations are possible by creating instances of Animation or AnimationTrigger. More information can be found in the GoJS Intro.