round off error

Math.log(1000) / Math.log(10) = 3, not 2.9999999999996

How do I make Javascript acknowledge this, even if I must lose the final digit?


I've tried this:


g = Math.log(a)/Math.log(b);
g = g * 10000000000000;
g = g + +0.0000000000005;
g = parseInt(g);
g = parseFloat(g / 10000000000000);

which is typical code for rounding. But it didn't work. I lost the final 6, but I still get a string of 9s.
Thanks!

Math.round(Math.log(1000)/Math.log(10))

Math.round(Math.log(1000)/Math.log(10))

Math.round() rounds to the nearest integer - OK here.

If you want to round a decimal number to (say) two decimal places:-

x = 3.7646386370435;
x = x * 100; // take it up two places
x = Math.round(x); // do the round
x = x/100; // take it back down two places
alert (x);

or

x = 3.764638638670435;
x = x.toFixed(2) * 1; // toFixed() converts to a string so multiply by 1 to revert to number if further processing is required. Omit if x to display only.
alert (x);


At least once per year, some group of scientists will become very excited and announce that whatever they announced last year about global warming is wrong.

Your first method works perfectly. Thanks!