Good memory. This is all at esdiscuss.org in the meeting notes, but I
can't google for ||= to save my life, even in Verbatim mode. Anyone?
Of course the original proposal is still in strawman stage on the wiki:
http://wiki.ecmascript.org/doku.php?id=strawman:default_operator
/be
Domenic Denicola <mailto:dome...@domenicdenicola.com>
February 9, 2014 at 12:49 PM
There was very active discussion, probably around 1.5 years ago, about
`||=` vs. a proposed `?=` (where `x ?= y` ≈ `x = x !== undefined ? x :
y`).
From what I recall some of the major points of discussion were:
- Should `?=` use `undefined` as its sentinel, or work with either
`null` or `undefined`? (This was before the behavior for default
parameters was decided.)
- Would adding `||=` be an attractive nuisance, when people "should"
be using `?=` instead?
- Given the existence of default parameters, and default destructuring
values, are either of these even necessary?
The last point, I think, was what killed both `?=` and `||=`. They
become much less necessary when you can write things like
```js
function f(foo = true, { bar = 5, baz = "ten" } = {}) {
console.log(foo, bar, baz);
}
```
From: es-discuss [mailto:es-discuss-boun...@mozilla.org] On Behalf Of
Andrea Giammarchi
Sent: Sunday, February 9, 2014 15:29
To: Hemanth H.M
Cc: es-discuss
Subject: Re: shorthand notation for attribute creation?
Unless I misunderstood your idea, `||=` makes me naturally think about
`+=` so if
`i += n;` means `i = i + n`
then
`o.name ||= value` means `o.name = o.name || value`
and this would be, according with all these years in ES3, the least
surprising behavior which is **way different** from checking if `name`
is not defined.
Accordingly, I wonder ...
1. what if `name` was inherited with a non _falsy_ value ?
2. what if `name` was defined as `undefined` ?
3. should that silently fail if `name` was already defined ?
Cheers
On Sun, Feb 9, 2014 at 2:17 AM, Hemanth H.M <hemanth...@gmail.com> wrote:
Something like `var foo = {}; foo.bar ||= 3` would be very useful.
But not sure how something like `obj['name']['maxlength']` be reduced
to shorthand check if 'name' is not defined.
Andrea Giammarchi <mailto:andrea.giammar...@gmail.com>
February 9, 2014 at 12:29 PM
Unless I misunderstood your idea, `||=` makes me naturally think about
`+=` so if
`i += n;` means `i = i + n`
then
`o.name <http://o.name> ||= value` means `o.name <http://o.name> =
o.name <http://o.name> || value`
and this would be, according with all these years in ES3, the least
surprising behavior which is **way different** from checking if `name`
is not defined.
Accordingly, I wonder ...
1. what if `name` was inherited with a non _falsy_ value ?
2. what if `name` was defined as `undefined` ?
3. should that silently fail if `name` was already defined ?
Cheers
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