Function constants for Identity and No-op

[Tiddo Langerak]

I think this is more about improving readability than saving a few 
characters.

On 08/10/2016 11:10 AM, Isiah Meadows wrote:
>
> I'll note that it's longer than just typing them out manually (and 
> close if they're aliased):
>
> ```js
> Function.IDENTITY
> IDENTITY
> x => x
>
> Function.NOOP
> NOOP
> () => {}
> ```
>
> Not sure if it adds anything.
>
>
> On Tue, Aug 9, 2016, 14:44 Eli Perelman <eli at eliperelman.com 
> <mailto:eli at eliperelman.com>> wrote:
>
>     I'm not sure if something like this has been proposed before, but
>     I often find myself declaring constants for the identity function
>     and the no-op function. I think it would be useful to have
>     constants available on Function containing these values. For
>     example `Function.IDENTITY` and `Function.NOOP`. Essentially these
>     constants would map to:
>
>     ```js
>     Function.IDENTITY = (a) => a;
>     Function.NOOP = () => null; // or:
>     Function.NOOP = () => {};
>     ```
>
>     These could then be used in places where non-user-controlled APIs
>     need default functions need to be executed, or as placeholders for
>     default values that may be executed before a function has been
>     supplied. For example:
>
>     ```js
>     // third-party API requires a callback or throws, but no
>     functionality really needs to done:
>     thirdParty.action(Function.NOOP);
>
>     // Function needs a default which *may* execute prior to having a
>     different one specified (contrived):
>     const action = (handler = Function.IDENTITY, value = 10)
>     =>handler(value);
>     ```
>
>     Thoughts? Seems like something simple with positive value. Thanks!
>
>     Eli Perelman
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