HN policy used to be that you could give items customized/more appropriate titles if the page you were linking to had a bad title.
In the last year, this guideline was removed from the guidelines page and mods have been renaming items "back" to the actual title of pages being linked to. So this item should be "fun.js" and now the useful title it is now. I'm surprised it hasn't happened yet because there have been a ton of examples in the past several months.
(If you couldn't guess, I think the change in policy is ridiculous.)
I have mixed feelings about it; on one hand, if an author titles a piece of work, then in the interest of honoring their creative expression (e.g. their work) then it'd be best to use their titles. Except, of course, when it's a poor title. On the other hand, authors aren't always the best about naming articles, and/or there's context that's present on their site that might produce a title that's out of context when lifted wholesale for use on another site.
For this article, I think "fun.js" is particularly poor, as it implies that it's about some coding project. Of course, the ecosystem has been tacking ".js" onto anything even remotely related to JS, and so it's not all the author's fault, but as a HN title it'd be misleading. IMO the 'best' title here would be akin to a reference, such as:
"Functional Javascript: Introducing Functional Programming with Underscore.js" by Michael Fogus (O'Reilly)
In the last year, this guideline was removed from the guidelines page and mods have been renaming items "back" to the actual title of pages being linked to. So this item should be "fun.js" and now the useful title it is now. I'm surprised it hasn't happened yet because there have been a ton of examples in the past several months.
(If you couldn't guess, I think the change in policy is ridiculous.)