Javascript math efficiency rounding

Question

Will this script

var a = 1/3;
var b = 2/5;
var c = a+b;

run faster or slower than this script

var a = Math.round(100*(1/3))/100;
var b = Math.round(100*(2/5))/100;
var c = a+b;

Or rather, is there a way to get javascript to evaluate an equation to only a certain level of accuracy.

var a = Math.onlySolveThisUpTo2DecimalPlaces(1/3); //0.33

Is the speed difference even large enough to care about?

I've had a question about `Math.round()` effeciency also. Consider bitshifting if speed is of upmost importance. See here: http://stackoverflow.com/questions/3233731/javascript-bitshift-alternative-to-math-round — cube, Feb 13 '14 at 22:21

score 3 · Accepted Answer · answered Feb 13 '14 at 21:25

Will this script […] run faster or slower than this script

Faster. There’s much more to do in the second.

Or rather, is there a way to get javascript to evaluate an equation to only a certain level of accuracy.

No.

Is the speed difference even large enough to care about?

No.

If you want to display the result with a certain precision, you can use a.toFixed(2) (two decimal places) or a.toPrecision(2) (two significant digits). But rounding (and not even to integers) isn’t going to positively affect performance.

Javascript math efficiency rounding

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