Rounding numbers down
JavaScript performance comparison
Info
Note that some of the listed alternatives to Math.floor()
use bitwise operators, which convert numbers to a 32bit sequence.
These alternatives will only work with positive signed 32bit floats, i.e. numbers from 0 to +2,147,483,647 (2^311
).
~~2147483647.1; // 2147483647
~~2147483648.1; // 2147483648
Preparation code
<script>
var n = Math.PI,
// 3.141592653589793
floorNew = (function() {
var f = Math.floor,
cap = 2 ^ 31;
return function(n) {
return n >= 0 && n < cap ? ~~n : f(n);
}
})();
</script>
Test runner
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Test  Ops/sec  

Math.floor 

pending… 
parseInt 

pending… 
Double bitwise NOT 

pending… 
Bitwise OR 

pending… 
Bitwise OR with 0 

pending… 
Bitwise AND 

pending… 
Bitwise left shift 

pending… 
Math.floor + ~~n 

pending… 
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Revisions
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to the URL. Here’s a list of current revisions for this page:
 Revision 1: published by Mathias Bynens and last updated
 Revision 2: published
 Revision 3: published and last updated
 Revision 4: published and last updated
 Revision 5: published by Jordan
 Revision 6: published by NilColor
 Revision 11: published
 Revision 12: published by Jack Rugile
 Revision 13: published
 Revision 14: published
 Revision 15: published
 Revision 18: published by Luin
 Revision 19: published by BigBossSNK
 Revision 22: published by David Simon
 Revision 23: published by eric lagergren
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