Set aria-labelledby & id attributes via JS

[Schepp]

Although it is nice to have that extra a11y piece in place I would suggest setting aria-labelledby and the corresponding id on a dialog's header part via JavaScript.

Why? I expect most people to copy & paste dialog code and to forget to adjust id and aria attributes accordingly. Also I suspect most users of your modal lib will not have the background needed to identify this problem.

By moving this part to JS you ensure a much better a11y across the board.

[anselmh]

I vote against. This is unexpected behavior for the user and should not be done in js. If aria is not used by developers this is a different problem which should be tackled other way.

[drublic]

Good points, @Schepp. Actually I think it is worth including a short note about changing the aria-labelledby in the How To Markup section.
I don't think it is necessary to include this as a JS method, users might remove the label's id anyway if they don't need them.