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

Rick Waldron waldron.rick at gmail.com
Mon Dec 3 14:54:53 PST 2012


On Mon, Dec 3, 2012 at 5:49 PM, Andrea Giammarchi <
andrea.giammarchi at gmail.com> wrote:

> fair enough ... but here there was a typo, right?
>
>  set.add( value ).forEach( item => ...send to some operation.... );
>

Possibly? s/item/value/ ?

Rick

>
>
> 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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