format-a-decimal-to-a-fixed-number-of-digits.md

Format A Decimal To A Fixed Number Of Digits

The Intl.NumberFormat object is a reliable way to format numbers in an i18n-friendly way. It available with Node and all modern browsers.

If I want to format number that I expect to contain decimals, I can do so by setting up a formatter using the decimal style.

const locale = "en-US";
const options = {
  style: "decimal",
};

const formatter = new Intl.NumberFormat(locale, options);

console.log(formatter.format(1234))
//=> 1,234
console.log(formatter.format(1234.5678))
//=> 1,234.568

Because of my locale (en-US), it adds a comma to deliniate the thousandth place. By default, it formats to three decimal places excluding decimals altogether if it is a whole number.

If I want to specify a fixed number of decimal places including for a whole number, I can use the minimumFractionDigits and maximumFractionDigits options.

const locale = "en-US";
const options = {
  style: "decimal",
  minimumFractionDigits: 2,
  maximumFractionDigits: 2,
};

const formatter = new Intl.NumberFormat(locale, options);

console.log(formatter.format(1234))
//=> 1,234.00
console.log(formatter.format(1234.5678))
//=> 1,234.57

Here, it includes the .00 on the whole number and it truncates the number with more than 2 decimal places rounding as necessary.

See the Intl.NumberFormat docs for more details.