CODEWITHSUNDEEP
javascript
RishiMath
RishiMath

Reputation: 193

Curious behavior of String()

I was just messing around with some code today, and I noticed that when I run String(null) or String(undefined), I get null and undefined respectively. But, when I checked the value I got for String([null, undefined]), I found it gave me "," as compared to the expected Result null,undefined. Does anyone have any idea on why this is happening? Since I didn't expect such behavior from String constructor on arrays, because as far as I have Noticed, the constructor simply put the values of every single one of the elements separated by commas.

Upvotes: 1

Views: 101

Answers (2)

AKX
AKX

Reputation: 169416

String(x) calls x.toString().

null and undefined values are represented by empty strings by Arrays' toString() since it calls Array.prototype.join() ("If element is undefined or null, let next be the empty String"):

> [null, undefined].toString()
","
> [null, null, null, null].toString()
",,,"

Upvotes: 6

Mateusz Krawczyk
Mateusz Krawczyk

Reputation: 308

You can use:

String([null, undefined].map(String));

or

[null, undefined].map(String).join()

Upvotes: 0

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