Method decodeNumber

src/Encoder/NumeralSystem.js:126–175

* Translates number from given system to decimal. * @protected * @param {string} type Numeral system to translate from * @param {string} string String representation * @return {Number|BigInt|null} Number, BigInt or null, if not defined

(type, string)

   * @return {Number|BigInt|null} Number, BigInt or null, if not defined
   */
  static decodeNumber (type, string) {
    // If BigInt is available, use it to treat arbitrarily large integers
    if (typeof BigInt !== 'undefined') {
      // See https://github.com/tc39/proposal-bigint/issues/86#issuecomment-348317283
      switch (type) {
        case 'binary':
          return BigInt(`0b${string}`)
        case 'octal':
          return BigInt(`0o${string}`)
        case 'decimal':
          return BigInt(string)
        case 'hexadecimal':
          return BigInt(`0x${string}`)
      }
    }

    // Fallback to limited JavaScript Numbers
    let number = null
    switch (type) {
      case 'binary':
        number = parseInt(string, 2)
        break
      case 'octal':
        number = parseInt(string, 8)
        break
      case 'decimal':
        number = parseInt(string, 10)
        break
      case 'hexadecimal':
        number = parseInt(string, 16)
        break
      case 'roman-numerals':
        number = NumeralSystemEncoder.romanNumeralsToDecimal(string)
        break
    }

    // Check for successful
    if (number === null || isNaN(number)) {
      return null
    }

    // Validate Number limits
    if (!NumeralSystemEncoder.isSafeInteger(number)) {
      throw new InvalidInputError(
        `Can't read '${string}' because the current environment does not ` +
        'support arbitrarily large integers.')
    }

    return number
  }

  /**
   * Exports number in the given system.