What is a javascript "[ <3 empty items> ]" structure?

Asked Apr 09 '20 at 15:37

Active Apr 09 '20 at 16:35

Viewed 203 times

I expect this JS:

(new Array(3)).map(_ => 3.14)

... to yield [3.14, 3.14, 3.14]. Instead, it yields [ <3 empty items> ]. My questions:

What on earth "is" this weird structure I've created? It would make sense to me if it were e.g. [undefined, undefined, undefined], but I don't know of a primitive JS structure called <empty item>. It's clearly not the same as [undefined, undefined, undefined], because the latter would have yielded [3.14, 3.14, 3.14].
How can I succinctly create an array [3.14, 3.14, 3.14]?

edited Apr 09 '20 at 15:39

asked Apr 09 '20 at 15:37

Magnus

1

`new Array(3).fill(3.14)` – Pointy Apr 09 '20 at 15:39
you can do `new Array(3).fill(3.14)`. If not you can fill it with `undefined` and then use `.map` like `new Array(3).fill(undefined).map` – SpiritOfDragon Apr 09 '20 at 15:41

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