How !+[] expression works in javascript

Question

I'm investigating why

!+[]

in javascript returns true. Do you have any idea?

`!+[]` can be interpreted as `NOT` of `Number` conversion of `String` value of `Array` i.e. `!(Number([].toString()))` = `!(Number(""))` = `!0` = `true` — Nikhil Aggarwal, Jun 22 '18 at 05:17
May I recommend - https://github.com/denysdovhan/wtfjs for more of these — Oorja, Jun 22 '18 at 05:21

score 2 · Accepted Answer · answered Jun 22 '18 at 05:14

2

+ is used to force numerical casting of a value and ! negates an expression.

So in this example it'd be

+[] = 0 !0 = true

answered Jun 22 '18 at 05:14

Lichwa

1 Answers1