Intl.NumberFormat.prototype.format()

numberFormat.format(number)

number

A Number or BigInt (en-US) to format.

The format getter function formats a number into a string according to the locale and formatting options of this NumberFormat (en-US) object.

Use the format getter function for formatting a single currency value, here for Russia:

var options = { style: 'currency', currency: 'RUB' };
var numberFormat = new Intl.NumberFormat('ru-RU', options);
console.log(numberFormat.format(654321.987));
// → "654 321,99 руб."

Use the format getter function for formatting all numbers in an array. Note that the function is bound to the NumberFormat (en-US) from which it was obtained, so it can be passed directly to Array.prototype.map.

var a = [123456.789, 987654.321, 456789.123];
var numberFormat = new Intl.NumberFormat('es-ES');
var formatted = a.map(numberFormat.format);
console.log(formatted.join('; '));
// → "123.456,789; 987.654,321; 456.789,123"

• Intl.NumberFormat (en-US)
• Number.prototype.toLocaleString()