Math.round vs hack

JavaScript performance comparison

Revision 52 of this test case created by Terry

Preparation code

<span>Result: </span>
<span id='result'>0</span>
<script>
  var somenum = -500 + (Math.random() * 1000),
      rounded, result = document.getElementById('result');
</script>
      
<script>
Benchmark.prototype.teardown = function() {
  result.innerHTML = rounded + '';

};
</script>

Preparation code output

<span>Result: </span> <span id='result'>0</span>

Test runner

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Testing in CCBot 2.0.0 / Other 0.0.0
Test Ops/sec
"proper" rounding
rounded = Math.round(somenum);
pending…
Hack rounding
rounded = ~~ (0.6 + somenum);
pending…
Proper hack rounding
rounded = ~~ (somenum + (somenum > 0 ? .5 : -.5));
pending…
Hack with bitwise OR
rounded = (0.5 + somenum) | 0;
pending…
Hack with bitwise shift
rounded = (0.5 + somenum) << 0;
pending…

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Revisions

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