Signum Function (all)
JavaScript performance comparison
Info
Derived from this question on StackOverflow: Number.sign() in JavaScript
Versions of the test: test everything — only numbers — only integers
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Preparation code
<script>
Benchmark.prototype.setup = function() {
// OUR TEST CODE (see other versions)
function test(sign) {
sign(1) // +1
sign(1908235) // +1
sign(.1e1) // 1
sign(Math.random()*21) // ??
sign(0) // 0
sign(0.00000) // 0
sign(+Infinity) // +1
sign(Infinity) // 1
sign(NaN) // 0 or NaN
// other types
sign("0")
sign("")
sign([])
sign("+23")
sign(null)
sign(undefined)
}
// 1. Obvious and fast
function sign1 (x) { return x > 0 ? 1 : x < 0 ? 1 : 0; }
// 1.1 Modification from kbec  one type cast less, more performant, shorter
function sign1b(x) { return x ? x < 0 ? 1 : 1 : 0; }
// 2. Elegant, short, not so fast
function sign2 (x) { return x && x / Math.abs(x); }
// (some issues with several cases, see answer.)
// 3. The art... but very slow
function sign3 (x) { return (x > 0)  (x < 0); }
// 4. Using bitshift
function sign4(x) { return (x >> 31) + (x > 0 ? 1 : 0); }
// 5. Typesafe:
function sign5 (x) {
return typeof x === 'number' ? x ? x < 0 ? 1 : 1 : x === x ? 0 : NaN : NaN;
}
// 5.1 Typesafe:
function sign5b (x) {
return (typeof x !== 'number'  isNaN(x)) ? NaN : (x ? x < 0 ? 1 : 1 : 0);
}
};
</script>
Test runner
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Test  Ops/sec  

1. Obvious 

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1.1. Not So Obvious 

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2. Elegant 

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3. Artistic 

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4. Bitshift 

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5. Safe 

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5. Safe v2 

pending… 
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Revisions
You can edit these tests or add even more tests to this page by appending /edit
to the URL. Here’s a list of current revisions for this page:
 Revision 1: published by Xavier Mendez
 Revision 2: published by Adam Hyland
 Revision 3: published by disfated
 Revision 5: published by disfated
 Revision 7: published by Bob
 Revision 9: published
 Revision 10: published
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 Revision 14: published
 Revision 15: published by mike2
 Revision 16: published by mike2
 Revision 17: published by mike2
 Revision 19: published
 Revision 20: published
 Revision 21: published by Joel Brage
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