mathjs/es/utils/bignumber/formatter.js

/**
 * Convert a BigNumber to a formatted string representation.
 *
 * Syntax:
 *
 *    format(value)
 *    format(value, options)
 *    format(value, precision)
 *    format(value, fn)
 *
 * Where:
 *
 *    {number} value   The value to be formatted
 *    {Object} options An object with formatting options. Available options:
 *                     {string} notation
 *                         Number notation. Choose from:
 *                         'fixed'          Always use regular number notation.
 *                                          For example '123.40' and '14000000'
 *                         'exponential'    Always use exponential notation.
 *                                          For example '1.234e+2' and '1.4e+7'
 *                         'auto' (default) Regular number notation for numbers
 *                                          having an absolute value between
 *                                          `lower` and `upper` bounds, and uses
 *                                          exponential notation elsewhere.
 *                                          Lower bound is included, upper bound
 *                                          is excluded.
 *                                          For example '123.4' and '1.4e7'.
 *                     {number} precision   A number between 0 and 16 to round
 *                                          the digits of the number.
 *                                          In case of notations 'exponential',
 *                                          'engineering', and 'auto',
 *                                          `precision` defines the total
 *                                          number of significant digits returned.
 *                                          In case of notation 'fixed',
 *                                          `precision` defines the number of
 *                                          significant digits after the decimal
 *                                          point.
 *                                          `precision` is undefined by default.
 *                     {number} lowerExp    Exponent determining the lower boundary
 *                                          for formatting a value with an exponent
 *                                          when `notation='auto`.
 *                                          Default value is `-3`.
 *                     {number} upperExp    Exponent determining the upper boundary
 *                                          for formatting a value with an exponent
 *                                          when `notation='auto`.
 *                                          Default value is `5`.
 *    {Function} fn    A custom formatting function. Can be used to override the
 *                     built-in notations. Function `fn` is called with `value` as
 *                     parameter and must return a string. Is useful for example to
 *                     format all values inside a matrix in a particular way.
 *
 * Examples:
 *
 *    format(6.4)                                        // '6.4'
 *    format(1240000)                                    // '1.24e6'
 *    format(1/3)                                        // '0.3333333333333333'
 *    format(1/3, 3)                                     // '0.333'
 *    format(21385, 2)                                   // '21000'
 *    format(12e8, {notation: 'fixed'})                  // returns '1200000000'
 *    format(2.3,    {notation: 'fixed', precision: 4})  // returns '2.3000'
 *    format(52.8,   {notation: 'exponential'})          // returns '5.28e+1'
 *    format(12400,  {notation: 'engineering'})          // returns '12.400e+3'
 *
 * @param {BigNumber} value
 * @param {Object | Function | number} [options]
 * @return {string} str The formatted value
 */
export function format(value, options) {
  if (typeof options === 'function') {
    // handle format(value, fn)
    return options(value);
  } // handle special cases


  if (!value.isFinite()) {
    return value.isNaN() ? 'NaN' : value.gt(0) ? 'Infinity' : '-Infinity';
  } // default values for options


  var notation = 'auto';
  var precision;

  if (options !== undefined) {
    // determine notation from options
    if (options.notation) {
      notation = options.notation;
    } // determine precision from options


    if (typeof options === 'number') {
      precision = options;
    } else if (options.precision) {
      precision = options.precision;
    }
  } // handle the various notations


  switch (notation) {
    case 'fixed':
      return toFixed(value, precision);

    case 'exponential':
      return toExponential(value, precision);

    case 'engineering':
      return toEngineering(value, precision);

    case 'auto':
      {
        // determine lower and upper bound for exponential notation.
        // TODO: implement support for upper and lower to be BigNumbers themselves
        var lowerExp = options && options.lowerExp !== undefined ? options.lowerExp : -3;
        var upperExp = options && options.upperExp !== undefined ? options.upperExp : 5; // handle special case zero

        if (value.isZero()) return '0'; // determine whether or not to output exponential notation

        var str;
        var rounded = value.toSignificantDigits(precision);
        var exp = rounded.e;

        if (exp >= lowerExp && exp < upperExp) {
          // normal number notation
          str = rounded.toFixed();
        } else {
          // exponential notation
          str = toExponential(value, precision);
        } // remove trailing zeros after the decimal point


        return str.replace(/((\.\d*?)(0+))($|e)/, function () {
          var digits = arguments[2];
          var e = arguments[4];
          return digits !== '.' ? digits + e : e;
        });
      }

    default:
      throw new Error('Unknown notation "' + notation + '". ' + 'Choose "auto", "exponential", or "fixed".');
  }
}
/**
 * Format a BigNumber in engineering notation. Like '1.23e+6', '2.3e+0', '3.500e-3'
 * @param {BigNumber | string} value
 * @param {number} [precision]        Optional number of significant figures to return.
 */

export function toEngineering(value, precision) {
  // find nearest lower multiple of 3 for exponent
  var e = value.e;
  var newExp = e % 3 === 0 ? e : e < 0 ? e - 3 - e % 3 : e - e % 3; // find difference in exponents, and calculate the value without exponent

  var valueWithoutExp = value.mul(Math.pow(10, -newExp));
  var valueStr = valueWithoutExp.toPrecision(precision);

  if (valueStr.indexOf('e') !== -1) {
    valueStr = valueWithoutExp.toString();
  }

  return valueStr + 'e' + (e >= 0 ? '+' : '') + newExp.toString();
}
/**
 * Format a number in exponential notation. Like '1.23e+5', '2.3e+0', '3.500e-3'
 * @param {BigNumber} value
 * @param {number} [precision]  Number of digits in formatted output.
 *                              If not provided, the maximum available digits
 *                              is used.
 * @returns {string} str
 */

export function toExponential(value, precision) {
  if (precision !== undefined) {
    return value.toExponential(precision - 1); // Note the offset of one
  } else {
    return value.toExponential();
  }
}
/**
 * Format a number with fixed notation.
 * @param {BigNumber} value
 * @param {number} [precision=undefined] Optional number of decimals after the
 *                                       decimal point. Undefined by default.
 */

export function toFixed(value, precision) {
  return value.toFixed(precision);
}