dojo7-formatting-currency-in-javascript

currency-formatter.coffee

Number.prototype.toCurrency = ->
  match = (this / 100).toString().match(/^-?(\d+)(\.\d+)?$/)
  return unless match

  cents = if match[2] then (match[2] + '00').substr(1, 2) else '00'
  dollars = match[1].replace(/(\d)(?=(\d\d\d)+(?!\d))/g, '$1,')

  result = "$#{dollars}.#{cents}"
  result = '-' + result if this < 0

  result

currency-formatter.js

Number.prototype.toCurrency = function() {
  var cents, dollars, match, result;

  match = (this / 100).toString().match(/^-?(\d+)(\.\d+)?$/);
  if (!match) return;

  cents = match[2] ? (match[2] + '00').substr(1, 2) : '00';
  dollars = match[1].replace(/(\d)(?=(\d\d\d)+(?!\d))/g, '$1,');

  result = "$" + dollars + "." + cents;
  if (this < 0) result = '-' + result;

  return result;
};

usage.js

// Examples
 433495.toCurrency(); // gives  $4,334.95
-433495.toCurrency(); // gives -$4,334.95