Return value of forEach

[Andrea Giammarchi]

That's usually a made-up issue ... the example code is using two maps
instead of computing the entire thing once in a composed function **and**
it already creates multiple copies of the initial Array.

Anyway, having `var log = DEBUG ? x => console.log(x) || x : x => x` in
means you could do this:

```js
const a = log([1, 2, 3]
  .map(square))
  .map(plus1)
  .reduce(add);
```

but again, we are using multiple maps and a reduce so if we want to be
realistic, and it's for debugging purpose only, I think using map would be
just fine.

Regards


On Fri, Oct 16, 2015 at 3:17 PM, Eric Devine <devineej at gmail.com> wrote:

> Array#map does the non-trivial operation of copying the entire array. In
> the example for loging to the console, this behavior is unintended. Perhaps
> an underscore-like tap method should be considered to be added to the Array
> prototype for these cases.
>
>
> On Fri, Oct 16, 2015 at 9:32 AM, Andrea Giammarchi <
> andrea.giammarchi at gmail.com> wrote:
>
>> Like I've written before, if you need to return an array you can use map
>> instead of forEach
>>
>> `arr.map(x => console.log(x) || x)`
>>
>> forEach has been like this since ever so while you wonder what kind of
>> code would look like based on the fact forEach doesn't return  anything, I
>> actually wonder how come there are still people expecting forEach to return
>> something.
>>
>> So, it would be a breaking change and actually it's not needed since you
>> have map.
>>
>> If the new Array, and for debugging purpose, is not desired, use `var log
>> = DEBUG ? x => console.log(x) || x : x => x` and abuse it as much as you
>> like.
>>
>> Would any of this work?
>>
>> Regards
>>
>>
>>
>> On Fri, Oct 16, 2015 at 2:23 PM, Niloy Mondal <niloy.mondal84 at gmail.com>
>> wrote:
>>
>>> > That'd be a compatibility break.
>>>
>>> Ugh... you mean people actually depend on `forEach` returning
>>> `undefined` (which it always does) to do further task?
>>>
>>> I wonder what that kinda code would look like >.<
>>>
>>> On Fri, Oct 16, 2015 at 6:08 PM, Frankie Bagnardi <f.bagnardi at gmail.com>
>>> wrote:
>>>
>>>> That'd be a compatibility break.
>>>>
>>>> If we end up getting :: though:
>>>>
>>>> ```js
>>>> function logEach(){
>>>>   this.forEach((x) => console.log(x));
>>>>   return this;
>>>> }
>>>>
>>>>
>>>> const a = [1, 2, 3]
>>>>   .map(square)
>>>>   ::logEach()
>>>>   .map(plus1)
>>>>   .reduce(add);
>>>> ```
>>>>
>>>> You could make that a global variable so you can sprinkle it around
>>>> your code in development.
>>>>
>>>> Having some developer tools in the language would be nice though. I
>>>> don't even think console.log is in the spec. A global like Debug.logThis
>>>> for example would be a more general ::-able.
>>>>
>>>>
>>>> On Fri, Oct 16, 2015 at 5:32 AM, Andrea Giammarchi <
>>>> andrea.giammarchi at gmail.com> wrote:
>>>>
>>>>> ```js
>>>>> const a = [1, 2, 3]
>>>>>   .map(square)
>>>>>   .map(x => console.log(x) || x )
>>>>>   .map(plus1)
>>>>>   .reduce(add);
>>>>> ```
>>>>>
>>>>> Regards
>>>>>
>>>>>
>>>>> On Fri, Oct 16, 2015 at 10:13 AM, Niloy Mondal <
>>>>> niloy.mondal84 at gmail.com> wrote:
>>>>>
>>>>>> Currently, `Array.prototype.forEach` returns `undefined`. It would be
>>>>>> more
>>>>>> useful if it returns the array itself.
>>>>>>
>>>>>> Say I have written some code like this...
>>>>>>
>>>>>> ```js
>>>>>> const a = [1, 2, 3]
>>>>>>   .map(square)
>>>>>>   .map(plus1)
>>>>>>   .reduce(add);
>>>>>> ```
>>>>>>
>>>>>> For some reason, I am not getting the expected output. For debugging,
>>>>>> I would
>>>>>> like the print the values after each step. My first initial reaction
>>>>>> is to
>>>>>> put a `forEach` step in between and print the values like so...
>>>>>>
>>>>>> ```js
>>>>>> const a = [1, 2, 3]
>>>>>>   .map(square)
>>>>>>   .forEach(x => console.log(x))
>>>>>>   .map(plus1)
>>>>>>   .reduce(add);
>>>>>> ```
>>>>>>
>>>>>> Unfortunately, this does not work as `forEach` returns `undefined`. I
>>>>>> now have
>>>>>> to comment out all the code below it. Having the _plug and play_
>>>>>> behaviour for
>>>>>> `forEach` would be very convenient.
>>>>>>
>>>>>> _______________________________________________
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>>>>>> es-discuss at mozilla.org
>>>>>> https://mail.mozilla.org/listinfo/es-discuss
>>>>>>
>>>>>>
>>>>>
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>>>>
>>>
>>
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