[javascript] Rounding numbers to 2 digits after comma

I have no idea how to do this? I'm adding comma numbers, result is of course always a number with way too many digits after the comma. anyone?

This is not really CPU friendly, but :

Math.round(number*100)/100

works as expected.

Previous answers forgot to type the output as an Number again. There is several ways to do this, depending on your tastes.

+my_float.toFixed(2)

Number(my_float.toFixed(2))

parseFloat(my_float.toFixed(2))

This worked for me:

var new_number = float.toFixed(2);

Example:

var my_float = 0.6666

my_float.toFixed(3) # => 0.667

Though we have many answers here with plenty of useful suggestions, each of them still misses some steps.
So here is a complete solution wrapped into small function:

function roundToTwoDigitsAfterComma(floatNumber) {
    return parseFloat((Math.round(floatNumber * 100) / 100).toFixed(2));
}

Just in case you are interested how this works:

1. Multiple with 100 and then do round to keep precision of 2 digits after comma
2. Divide back into 100 and use toFixed(2) to keep 2 digits after comma and throw other unuseful part
3. Convert it back to float by using parseFloat() function as toFixed(2) returns string instead

Note: If you keep last 2 digits after comma because of working with monetary values, and doing financial calculations keep in mind that it's not a good idea and you'd better use integer values instead.

I use this:

function round(value, precision) {_x000D_
_x000D_
 if(precision == 0)_x000D_
  return Math.round(value);   _x000D_
_x000D_
 exp = 1;_x000D_
 for(i=0;i<precision;i++)_x000D_
  exp *= 10;_x000D_
_x000D_
 return Math.round(value*exp)/exp;_x000D_
}

use the below code.

alert(+(Math.round(number + "e+2")  + "e-2"));

UPDATE: Keep in mind, at the time the answer was initially written in 2010, the bellow function toFixed() worked slightly different. toFixed() seems to do some rounding now, but not in the strictly mathematical manner. So be careful with it. Do your tests... The method described bellow will do rounding well, as mathematician would expect.

• toFixed() - method converts a number into a string, keeping a specified number of decimals. It does not actually rounds up a number, it truncates the number.
• Math.round(n) - rounds a number to the nearest integer. Thus turning:

0.5 -> 1; 0.05 -> 0

so if you want to round, say number 0.55555, only to the second decimal place; you can do the following(this is step-by-step concept):

• 0.55555 * 100 = 55.555
• Math.Round(55.555) -> 56.000
• 56.000 / 100 = 0.56000
• (0.56000).toFixed(2) -> 0.56

and this is the code:

(Math.round(number * 100)/100).toFixed(2);