lib/formatNumber.js

import objectAssign from 'object-assign';

import stripInsignificantZeros from './internal/stripInsignificantZeros';
import settings from './settings';
import toFixed from './toFixed';

/**
 * Format a number, with comma-separated thousands and custom precision/decimal places.
 *
 * _Alias_: `format(number, opts)`
 *
 * **Usage:**
 *
 * ```js
 * // Default usage
 * formatNumber(5318008);
 * // => 5,318,008
 *
 * // Custom format
 * formatNumber(9876543.21, { precision: 3, thousand: " " });
 * // => 9 876 543.210
 * ```
 *
 * @access public
 * @param {Number} number - Number to be formatted
 * @param {Object} [opts={}] - Object containing all the options of the method
 * @return {String} - Given number properly formatted
  */
function formatNumber(number, opts = {}) {
  // Resursively format arrays:
  if (Array.isArray(number)) {
    return number.map((val) => formatNumber(val, opts));
  }

  // Build options object from second param (if object) or all params, extending defaults
  opts = objectAssign({},
    settings,
    opts
  );

  // Do some calc
  const negative = number < 0 ? '-' : '';
  const base = parseInt(toFixed(Math.abs(number), opts.precision), 10) + '';
  const mod = base.length > 3 ? base.length % 3 : 0;

  // Format the number
  const formatted = negative +
    (mod ? base.substr(0, mod) + opts.thousand : '') +
      base.substr(mod).replace(/(\d{3})(?=\d)/g, '$1' + opts.thousand) +
        (opts.precision > 0 ? opts.decimal + toFixed(Math.abs(number), opts.precision).split('.')[1] : '');

  return opts.stripZeros ? stripInsignificantZeros(formatted, opts.decimal) : formatted;
}

export default formatNumber;