How to set the transition from one value to another in d3.js?

Question

JavaScript

I have a schedule . I need to animate it so that when the page loads, the blue and blue parts of the graph would appear alternately (for example, first the blue one appeared and took the length it needed, and then the blue one the same way). As far as I understand, the d3 spec needs to be set to animation after the elements have already been drawn. That is, on line 49 I have

g.transition();
//условия анимации

But I have no idea how to set this animation correctly.
For the second day I can not solve this issue. Help, who worked with d3.js.

Answer 1

Updates, Transitions, and Motion