Any advantage to using variable with tilde in javascript vs. -1?

Question

Other than a slight performance gain, is there an advantage to using !~x as true vs. checking to see if ~-1 ?

`if (~someString.indexOf(someOtherString)){...}` is nice, but not always clear. — Shmiddty, May 31 '13 at 20:37
`~1` is `-2`, `~~X` can be used to do a 'floor' on `X` (where X is positive) — Shmiddty, May 31 '13 at 20:43
What do you mean by _"checking to see if ~-1"_? Is your question `~x` vs `x != -1`? — Eric, May 31 '13 at 20:48

score 3 · Answer 1 · answered May 31 '13 at 20:51

3

There can be a difference for large numbers. Because you're confined to a 32-bit range, consider the following.

var x = Math.pow(2,32)-1; // 4294967295

console.log(~x); // 0

So here you get a 0 result giving you the opposite boolean conversion than you'd expect.

answered May 31 '13 at 20:51

2

Still not sure if this answers the question, because I'm not sure what the question actually is. :( – Shmiddty May 31 '13 at 20:52
@Shmiddty: I'm pretty sure your comment under the question describes what the asker is getting at. But if this is an Array or Array-like collection that can have very high indices, there can be an unexpected results. – May 31 '13 at 20:56
1

I definitely +1'd this because it's a good thing to note. – Shmiddty May 31 '13 at 21:08

score 0 · Answer 2 · answered May 31 '13 at 20:43

0

There's no behavioral difference. Use whichever is clearest for the scenario you're implementing.

answered May 31 '13 at 20:43

Chris Tavares

2 Answers2