performance - Javascript Math.ceil(Math.abs()) optimization

Question

I'm using Math.ceil( Math.abs( x ) ) inside a loop.

Can anyone realize any optimization for this operation? (Bitwise or what?)

You are welcome to benchmark at jsperf.com

Answer 1

Math.abs doesn't get simpler according to webkit JavaScriptCore

case MathObjectImp::Abs:
result = ( arg < 0 || arg == -0) ? (-arg) : arg;

However ceil uses C's ceil function

 case MathObjectImp::Ceil:
    result = ::ceil(arg);

so testing on JSpref http://jsperf.com/math-ceil-vs-bitwise bitwise is faster
testing @orangedog's answer http://jsperf.com/math-ceil-vs-bitwise/2 Math.ceil is faster

So I guess your best choice is:

var n = Math.abs(x);
var f = (n << 0),
f = f == n ? f : f + 1;