Format a number with commas or custom character

Usage no npm install needed!

<script type="module">
  import commaNumber from '';


Comma number

Build Status npm version Coverage Status


$ npm install --save comma-number


const commaNumber = require('comma-number')

commaNumber(1000) // "1,000"
commaNumber(-1000) // "-1,000"
commaNumber(-1000, '.') // "-1.000"

commaNumber(1000.12) // "1,000.12"
commaNumber(-1000.12) // "-1,000.12"
commaNumber('-1000,12', '.', ',') // "-1.000,12"

// make a new function using custom separator and decimal char:
const format = commaNumber.bindWith('_', '!')
// use it as you would commaNumber().
format(1000)     // "1_000"
format(-1000)    // "-1_000"
format(1000.12)  // "1_000!12"
format(-1000.12) // "-1_000!12"

Version 2 Changes

Revised implementation changes the API a bit:

  1. input with a type other than string and number is returned as is, not as '0'.
  2. supports decimals in the number
  3. a string number may use an alternate decimal character, specify it as the third argument
  4. added a bindWith function to use a currying style to bind options for a reusable format function.

Other changes:

  1. Added benchmarking to test implementation performance
  2. added code coverage
  3. added new badges in this README
  4. added more versions to the Travis CI config


commaNumber(number, [separator=','], [decimalChar='.'])


  • number : {(Number|String)} Number to format
  • separator : {String} Value used to separate numbers
  • decimalChar : {String} Value used to separate the decimal value


  • {String} Comma formatted number

bindWith(separator, decimalChar)

The commaNumber function accepts these same parameters as the second and third params. This prevents using currying to bind them and reuse that bound function.

The bindWith function accepts the options and returns a function bound with them.

// the default commaNumber uses a comma separator and period for decimal char.
var commaNumber = require('comma-number')
  // can build a custom version using bindWith.
  , format = commaNumber.bindWith('_', '!')
  , result1 = commaNumber(1234567.89)
  , result2 = format('1234567.89')

console.log(result1) // outputs:  1,234,567.89
console.log(result2) // outputs:  1_234_567!89

Scripts for Testing, Benchmarking, and Code Coverage

# run tests via tap
$ npm test

# benchmark current implementation versus previous
npm run benchmark

# get coverage info by default with testing:
npm test

Performance Comparison

The rewrite has a considerable performance increase from the previous version.

I converted the benchmark output from my machine into a table.

It compares the performance of version 1.1.0 with 2.0.0. The inputs with decimals can only be processed by the new version so those show as "invalid" for the previous version.

MIT License