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FROM WITHIN THE PEN ITSELF?

Filip Kis needed that. I think the idea is that it's a unique identifier, so if you need that for something programmatic (perhaps a unique key for Firebase or something), you got it. It also ensures that forks will also use their own unique key.

Here's the solution:

See the Pen CodePen ID Function by Filip Kis (@filipkis) on CodePen.

Perhaps one day we can start providing data like that in an easier-to-access way, but it bears some consideration. Inserting a global seems a little obtrusive.