roundCommaString = function (input, decimals) {
  if (isNaN(input)) { return 0; }

  if (!decimals) { decimals = 0; }
  return commaString(round(input, decimals).toFixed(decimals));
}
Rounds a number then adds commas so it's easier to read

@example
'{{ 123456789 | roundCommaString }}'
this.$options.filters.roundCommaString(123456789);

@param {int} input     The number to add commas to
@param {int} decimals  The number of decimals to preserve, default = 0
@returns {string}      The number string with commas