Array.create and Function.create

Sultan thysultan at
Thu Jan 10 08:07:50 UTC 2019

>An array with no prototype wouldn't have any of the iteration methods on

Yes, that is what is intended with this, similar to an Object.create(null)
object with number-ed keys.

Alternatively one could look at the objects created from this to be the
"bare-bones" structure around these data-structures.

That is the in-existence of prototypes and own properties like "length"
makes it clear that these "flat" objects are intended as author managed

There are is no visible default prototype or own properties because the
author will create, expose and managed these for the data-structure
explicitly if need be or more commonly choose to not expose the
data-structure at all and use these for low-level internal book keeping for
other abstractions.

This would create a new ceiling(or ground-level) for how "low-level" one
could go with JavaScript if these where part for the language and as a
secondary consequence allow engines to make stronger assumptions with
regards to operations on these structs.

On Thu, Jan 10, 2019 at 9:48 AM Jordan Harband <ljharb at> wrote:

> An array with no prototype wouldn't have any of the iteration methods on
> it; a function with no prototype wouldn't have .call/.bind/.apply - length
> and name are own properties of functions, and length is an own property of
> an array, so you'd get those regardless.
> (`Array.from({ length: 1000 })` already creates an array of length 1000
> without holes, fwiw)
> On Wed, Jan 9, 2019 at 10:43 PM Sultan <thysultan at> wrote:
>> Identical to Object.create but for Arrays and Functions.
>> This method will allow you to create arrays with no prototype.
>> This would allow authors the ability to use array objects as state
>> containers without the need to resort to index-based objects with
>> Object.create(null, length)
>> When you want to both use an array-like struct as both a property and
>> index-able map.
>> A side-effect of this would afford engines a strong heuristic for
>> avoiding holey-array look-ups operations when there's no prototype to walk.
>> For example the following would create an array with a length of 1000
>> without "holes".
>> const arr = Array.create(null, 1000)
>> In addition this could also apply to functions with
>> Function.create(null, () => {})
>> When you want to use functions as state-containers but don't want any of
>> the implicit properties(length, name) etc.
>> _______________________________________________
>> es-discuss mailing list
>> es-discuss at
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the es-discuss mailing list