`null` and default arguments

# Isiah Meadows (10 years ago)

I know it's a little late for this, but what was the rationale of using only undefined instead of both that and null to denote omitted values for optional arguments in ES6? Before this change, it was a frequent idiom to check optional arguments via == null instead of === undefined and pass null as the argument to denote the absence of a value.

Just a curious question.

I know it's a little late for this, but what was the rationale of using
only `undefined` instead of both that and `null` to denote omitted values
for optional arguments in ES6? Before this change, it was a frequent idiom
to check optional arguments via `== null` instead of `=== undefined` and
pass `null` as the argument to denote the absence of a value.

Just a curious question.
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# Brendan Eich (10 years ago)

See esdiscuss.org/topic/default-operator-strawman-rather-than#content-13 and surrounding thread.

See 
https://esdiscuss.org/topic/default-operator-strawman-rather-than#content-13 
and surrounding thread.

/be

Isiah Meadows wrote:
>
> I know it's a little late for this, but what was the rationale of 
> using only `undefined` instead of both that and `null` to denote 
> omitted values for optional arguments in ES6? Before this change, it 
> was a frequent idiom to check optional arguments via `== null` instead 
> of `=== undefined` and pass `null` as the argument to denote the 
> absence of a value.
>
> Just a curious question.
>
> _______________________________________________
> es-discuss mailing list
> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss

# Isiah Meadows (10 years ago)

Thanks! I understand now.

Thanks! I understand now.

On Mon, Aug 17, 2015, 17:16 Brendan Eich <brendan at mozilla.org> wrote:

> See
>
> https://esdiscuss.org/topic/default-operator-strawman-rather-than#content-13
> and surrounding thread.
>
> /be
>
> Isiah Meadows wrote:
> >
> > I know it's a little late for this, but what was the rationale of
> > using only `undefined` instead of both that and `null` to denote
> > omitted values for optional arguments in ES6? Before this change, it
> > was a frequent idiom to check optional arguments via `== null` instead
> > of `=== undefined` and pass `null` as the argument to denote the
> > absence of a value.
> >
> > Just a curious question.
> >
> > _______________________________________________
> > es-discuss mailing list
> > es-discuss at mozilla.org
> > https://mail.mozilla.org/listinfo/es-discuss
>
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