[webkit-dev] Preferred style for checking for undefined in our built-in JavaScript code?

Filip Pizlo fpizlo at apple.com
Mon Nov 30 11:39:38 PST 2015

I’ve also been guilty of:

	if (xxx === void 0)

This is slightly better than saying “undefined”, since that’s not actually a reserved word.

I believe that all of these should perform the same.  We should pick one based on what looks nicest and what has the most clear semantics.


> On Nov 30, 2015, at 11:37 AM, Darin Adler <darin at apple.com> wrote:
> I see the following in some code:
>    if (xxx === undefined)
> And I see the following in some other code:
>    if (typeof xxx == “undefined”)
>    or
>    if (typeof xxx === “undefined”)
> Is one preferred over the other, style-wise? Is one more efficient than the other?
> — Darin
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