(Map|Set|WeakMap)#set() returns `this` ?

Andrea Giammarchi andrea.giammarchi at gmail.com
Mon Dec 3 14:49:31 PST 2012


fair enough ... but here there was a typo, right?

 set.add( value ).forEach( item => ...send to some operation.... );

Thanks


On Mon, Dec 3, 2012 at 2:44 PM, Rick Waldron <waldron.rick at gmail.com> wrote:

>
>
>
> On Mon, Dec 3, 2012 at 5:21 PM, Andrea Giammarchi <
> andrea.giammarchi at gmail.com> wrote:
>
>> 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 )
>>
>
> A collection is a 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 ...
>>
>
> You're completely ignoring the iterator APIs and forEach—either of which a
> program might want to call on an object post-mutation:
>
> Add value to the Set and...
>
> - get a fresh iterable for the values (or keys, or entries):
>
>   set.add( value ).values();
>
> - send each value in the set to another operation:
>
>   set.add( value ).forEach( item => ...send to some operation.... );
>
> - spread into an array of unique items:
>
> [ ...set.add(value) ]; // always unique! yay!
>
>
> Add a key and value to the Map and...
>
> - get a fresh iterable for the keys (or values, or entries)
>
>   map.set( key, val ).keys();
>    map.set( key, val ).values();
>   map.set( key, val ).entries();
>
> - send each to pair to another operation (see above)
>
> - spread into an array of pairs (see above)
>
>
> Being able to express the complete operation and get mutated object back
> at once is a compelling use case.
>
> Rick
>
>
>>
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