Question on Learn D3: Animation

[miles]

On this page:

Learn D3: Animation

What is the purpose of this line?:

const zx = x.copy(); // x, but with a new domain.

I assume the copy is to prevent mutations of x, but I don’t see where mutations are happening in that cell. Things seem to work fine if that line is eliminated and all zx is replaced with x.

Is there a better way to ask these types of questions or propose changes? Pull requests are a nice way to provide some context. Is that workflow available? (I see that’s been proposed in Notebook pull requests). Also, is it possible to share an anchored URL link to a particular cell?

[mootari]

@miles

Things seem to work fine if that line is eliminated and all zx is replaced with x

In this case, yes. But if you had another cell that also modifies x, you’d be in for surprises.

In Observable you’ll want to avoid side effects (a cell modifying another cell) whenever possible. I would view this as a best practice example, especially since code is often copied verbatim.

@miles

Is there a better way to ask these types of questions or propose changes?

This forum is a great place to ask for help, but you can also directly add a comment to a notebook.

@miles

Also, is it possible to share an anchored URL link to a particular cell?

You can only link directly to named cells. To get the anchored link, click on a cell’s menu: