I'm not a person of influence, but as a JS developer, I agree with Andrea on
this. I think Map#set() should return the value. I would expect the same
behavior as obj[key] = value. I find Andrea's use case (m.get(k) || m.set(k,
v)) more compelling than the method chaining possibilities.
Nathan
Date: Mon, 3 Dec 2012 14:21:24 -0800
Subject: Re: (Map|Set|WeakMap)#set() returns `this` ?
From: andrea.giammar...@gmail.com
To: waldron.r...@gmail.com
CC: es-discuss@mozilla.org
IMHO, a set(key, value) should return the value as it is when you address a
value
var o = m.get(k) || m.set(k, v); // o === v
// equivalent of
var o = m[k] || (m[k] = v); // o === v
a set with a key that returns `this` is a non case so almost as useless as the
void return is.
Usefulness comes with use cases ... except this jQuery chainability thingy that
works fine for jQuery structure ( an ArrayLike Collection ) who asked for
map.set(k0, v0).set(k1, v1).set(k2, v2) ? Or even map.set(k0,v0).get(k1) ? what
are use cases for this?
I am honestly curious about them because I cannot think a single one ...
specially with the Set
s.add(k0).add(k1).add(k2) ... this code looks weird inlined like this ...
Thanks for your patience
On Mon, Dec 3, 2012 at 2:04 PM, Rick Waldron <waldron.r...@gmail.com> wrote:
On Mon, Dec 3, 2012 at 4:28 PM, Andrea Giammarchi <andrea.giammar...@gmail.com>
wrote:
I wonder what was the use case that convinced TC39 to return `this` with these
methods.
Assuming you read the notes, I proposed the agenda item based on the best
practice of ensuring meaningful returns, and in the case of mutation methods,
|this| is a meaningful return.
Accordingly, this will never work:var query = map.has('queried') ?
map.get('queried') : map.set('queried', $('myquery'));
Previously, map.set() had a useless void return...
And it will be something like:var query = map.has('queried') ?
map.get('queried') : map.set('queried', $('myquery')).get('queried');
which is ugly and I don't really understand where map.set(k0, v0).set(k1,
v1).set(k2, v2) could be useful.
Accessing the object post-mutation allows for more expressive use of the API.
Rick
Thanks for clarifications ( a use case would be already good )
br
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