shorthand notation for attribute creation?

Domenic Denicola domenic at domenicdenicola.com
Sun Feb 9 12:49:33 PST 2014


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-bounces at 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.hm at 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.




-- 
'I am what I am because of who we all are'
h3manth.com
-- Hemanth HM 

_______________________________________________
es-discuss mailing list
es-discuss at mozilla.org
https://mail.mozilla.org/listinfo/es-discuss



More information about the es-discuss mailing list