Why is 1 + + + 1 = 2 in Javascript?
What is this behavior called? Is it documented somewhere?
Thanks.
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stackoverflow.com/questions/971312/…Sudhir Bastakoti– Sudhir Bastakoti2011-12-30 01:14:56 +00:00Commented Dec 30, 2011 at 1:14
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@Sudhir: Interestingly enough, though, there is no ++ here.Thilo– Thilo2011-12-30 01:20:01 +00:00Commented Dec 30, 2011 at 1:20
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2 Answers
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.
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It's parsed as...
1 + (+ (+ 1))
...which obviously evaluates to two.
