csw5-base26-final.js

/**
 * A set of static methods governing string-to-int conversion
 * in base26. In base26, only lowercase alpha chars [a-z]
 * are valid and map to an integer range (0, 26]
 */
module.exports = {
  /**
   * returns the base26 integer corresponding with the provided char. Note
   * that by design uppercase chars may be supplied, and are
   * treated as lowercase. If a string containing more than one char is
   * supplied, only the first char (0 index) is considered.
   *
   * @param {string} char
   * @returns {number} (0, 26]
   */
  getBase26Digit: (char) => {
    let normalized = char.toLowerCase().charCodeAt(0) - 97
    if (normalized <= 25 && normalized >= 0) { return normalized }
    else { throw new Error('not base 26') }
  },

  /**
   * returns a lowercase alpha char [a-z] corresponding with the provided integer.
   * If the provided integer is outside the range of (0, 26], an error will be thrown.
   *
   * @param {number} digit - a number in the range (0, 26]
   * @throws will throw an error if the digit param is outside (0, 26]
   * @returns {string} [a-z]
   */
  getUTF16: (digit) => {
    if (digit < 0 || digit > 25) { throw new Error('not base 26') }
    return String.fromCharCode(digit + 97)
  }
}