What is the difference between Array.function and Array.prototype.function?

Question

I've found that some functions like concat() push() every() both exist in Array and Array.prototype(with firefox 57.0.1 console)

It's confusing since prototype methods exist in Array.
Additionally, where does staic method(Array.from(), Array.isArray() etc) exists in?

I think I've understood concepts of javascript prototype to some extent, so what I'm curious about is why prototype methods(concat() push() ...) apear both in Array and Array.prototype

@Kris no, it's not a duplicate. Firefox really does have additional methods that are not part of the prototype. — Alnitak
– Alnitak, Commented Dec 7, 2017 at 9:06
Ok sorry you are right, got trapped the same way like all the upvoters from the second answer... — Kris
– Kris, Commented Dec 7, 2017 at 9:15

Alnitak · Accepted Answer · 2017-12-07 09:23:26Z

4

Firefox's Array function appears to have additional (non-conformant) "static" methods that replicate the prototype methods except that they take the array as the first parameter instead of via the implicit this context.

To see those methods and properties of Array, use:

Object.getOwnPropertyNames(Array)

In Firefox you'll (mostly) see the same list as in your first screenshot. I haven't yet figured out why Array.isArray is missing in your list, but it does appear in my Firefox 57.

In Chrome you'll only see the ES6 mandated "static" methods (i.e. Array.from, Array.isArray, Array.of) and the standard properties.

edited Dec 7, 2017 at 9:23

answered Dec 7, 2017 at 8:59

Alnitak

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7 Comments

soonoo Over a year ago

My firefox also shows Array.isArray with Object.getOwnPropertyName(Array) however does not show with just console.log(Array) How about you?

Alnitak Over a year ago

@soonoo Likewise, it doesn't appear in the console.log output, but it does appear in the object inspector pane. Perhaps it's a bug in the console?

soonoo Over a year ago

Thanks but still confused ㅠㅠ

Alnitak Over a year ago

@soonoo what's the confusion?

soonoo Over a year ago

it's not your answer, just about firefox's non-general behavior

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