Why is 1 + + + 1 = 2 in Javascript?
What is this behavior called? Is it documented somewhere?
Thanks.
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http://stackoverflow.com/questions/971312/why-avoid-increment-and-decrement-operators-in-javascript – Sudhir Bastakoti Dec 30 '11 at 01:14
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@Sudhir: Interestingly enough, though, there is no ++ here. – Thilo Dec 30 '11 at 01:20
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It's because of the spacing. The unary operator + can be applied as many times as necessary, and so your expression becomes:
1 + (+(+1))
That is,
1 + 1
. Normally, it appears you can't do this, i.e. 1 + ++ 1 will fail, but that's because two +s are parsed as a prefix increment which is invalid when not used on a variable. In the same way, 1 +++ 1 fails because it's parsed as 1++ + 1, and you can't increment 1.
Ry-
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It's parsed as...
1 + (+ (+ 1))
...which obviously evaluates to two.
Marcelo Cantos
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