> Even if it's used on one place only, isn't it still useful?

To be honest, there is two places (forgot this one: https://github.com/firebug/firebug/blob/0df15bc266321a3f61a2911214e3f46664186102/extension/content/firebug/console/commandLine.js#L1140). Two `for (in)` then.

> I think not having this as a lib is fine, because for (in) loops are very clear in what they do.

I agree. 

Florent