Function parseNumber

packages/common/src/i18n/format_number.ts:401–455

* Parses a number. * Significant bits of this parse algorithm came from https://github.com/MikeMcl/big.js/

(num: number)

 * Significant bits of this parse algorithm came from https://github.com/MikeMcl/big.js/
 */
function parseNumber(num: number): ParsedNumber {
  let numStr = Math.abs(num) + '';
  let exponent = 0,
    digits,
    integerLen;
  let i, j, zeros;

  // Decimal point?
  if ((integerLen = numStr.indexOf(DECIMAL_SEP)) > -1) {
    numStr = numStr.replace(DECIMAL_SEP, '');
  }

  // Exponential form?
  if ((i = numStr.search(/e/i)) > 0) {
    // Work out the exponent.
    if (integerLen < 0) integerLen = i;
    integerLen += +numStr.slice(i + 1);
    numStr = numStr.substring(0, i);
  } else if (integerLen < 0) {
    // There was no decimal point or exponent so it is an integer.
    integerLen = numStr.length;
  }

  // Count the number of leading zeros.
  for (i = 0; numStr.charAt(i) === ZERO_CHAR; i++) {
    /* empty */
  }

  if (i === (zeros = numStr.length)) {
    // The digits are all zero.
    digits = [0];
    integerLen = 1;
  } else {
    // Count the number of trailing zeros
    zeros--;
    while (numStr.charAt(zeros) === ZERO_CHAR) zeros--;

    // Trailing zeros are insignificant so ignore them
    integerLen -= i;
    digits = [];
    // Convert string to array of digits without leading/trailing zeros.
    for (j = 0; i <= zeros; i++, j++) {
      digits[j] = Number(numStr.charAt(i));
    }
  }

  // If the number overflows the maximum allowed digits then use an exponent.
  if (integerLen > MAX_DIGITS) {
    digits = digits.splice(0, MAX_DIGITS - 1);
    exponent = integerLen - 1;
    integerLen = 1;
  }

  return {digits, exponent, integerLen};
}

/**
 * Round the parsed number to the specified number of decimal places