Arbitrary Base Converter

arbitrary-base-converter.js

const Alphabet = {
  BINARY:        '01',
  OCTAL:         '01234567',
  DECIMAL:       '0123456789',
  HEXA_DECIMAL:  '0123456789abcdef',
  ALPHA_LOWER:   'abcdefghijklmnopqrstuvwxyz',
  ALPHA_UPPER:   'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
  ALPHA:         'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ',
  ALPHA_NUMERIC: '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
};

function baseConverter(input, source, target) {
  if (source === target) { return input; }
  //console.log(input);
  //console.log(source, target);
  let remainders = [];
  let div = 0;
  if ((source.length === 2 && target.length !== 10) || (source.length === 2 && !Number.isSafeInteger(parseInt(input)))) {
    /*
    *  convert bin to dec first
    *  if bin should be converted to not dec
    *  or if bin is not a safe integer
    */
    let binToDec = 0;
    let power = 0;
    for (let i = input.length - 1; i >= 0; i--) {
      binToDec += parseInt(input[i]) * Math.pow(2, power);
      power++;
    }
    input = binToDec;
    if (!Number.isSafeInteger(parseInt(input)) && target.length === 10) {
      /* 
      *  if input is not a safe integer
      *  and should actually be converted from bin to dec
      */
      return input;
    }
  } else if (source.length !== 2 && source.length !== 10) {
    /*
    *  use dictionary to convert from arbitrary base
    *  to base10 before moving further
    */
    //console.log('convert:', input, 'from:', source, 'to decimal');
    const sourceBase = source.length;
    let sourceToBase10 = 0;
    //console.log('sourceBase:', sourceBase);
    let power = 0;
    for (let i = input.length - 1; i >= 0; i--) {
      sourceToBase10 += source.indexOf(input[i]) * Math.pow(sourceBase, power);
      power++;
    }
    input = sourceToBase10;
    //input = input.split('').map(item => source.indexOf(item)).join('');
  }
  //console.log('input:', input);
  input = parseInt(input);
  while (input > target.length) {
    /*
    *  convert using remainder approach
    */
    const remainder = input % target.length;
    remainders.unshift(remainder);
    input = Math.trunc(input / target.length);
    //console.log('input:', input, '| remainder:', remainder);
  }
  //console.log('remainders:', remainders, '| input:', input);
  if (source.length === 10 && target.length === 2) {
    /*
    *  fixt for dec to bin convertion
    *  convert rest if input is still >= 2
    */
    while (input >= target.length) {
      /*
      *  convert using remainder approach
      */
      const remainder = input % target.length;
      remainders.unshift(remainder);
      input = Math.trunc(input / target.length);
      //console.log('input:', input, '| remainder:', remainder);
    }
  }
  remainders.unshift(input);
  //console.log('remainders:', remainders);
  remainders = remainders.map(item => target[item]);
  return remainders.join('');
}

// convert between numeral systems
baseConverter('15', Alphabet.DECIMAL, Alphabet.BINARY); // '1111'
baseConverter('15', Alphabet.DECIMAL, Alphabet.OCTAL); // '17'
baseConverter('1010', Alphabet.BINARY, Alphabet.DECIMAL); // '10'
baseConverter('1010', Alphabet.BINARY, Alphabet.HEXA_DECIMAL); // 'a'

// other bases
baseConverter('0', Alphabet.DECIMAL, Alphabet.ALPHA); // 'a'
baseConverter('27', Alphabet.DECIMAL, Alphabet.ALPHA_LOWER); // 'bb'
baseConverter('hello', Alphabet.ALPHA_LOWER, Alphabet.HEXA_DECIMAL); // '320048'
baseConverter('SAME', Alphabet.ALPHA_UPPER, Alphabet.ALPHA_UPPER); // 'SAME'

// advanced
baseConverter('1001001100101100000001011010010', Alphabet.BINARY, Alphabet.DECIMAL); // '1234567890'
baseConverter('1001001100101100000001011010010', Alphabet.BINARY, Alphabet.OCTAL); // '11145401322'
baseConverter('1001001100101100000001011010010', Alphabet.BINARY, Alphabet.HEXA_DECIMAL); // '499602d2'
baseConverter('1001001100101100000001011010010', Alphabet.BINARY, Alphabet.ALPHA_LOWER); // 'dzxprwk'
baseConverter('1001001100101100000001011010010', Alphabet.BINARY, Alphabet.ALPHA); // 'dmSkYk'
baseConverter('1001001100101100000001011010010', Alphabet.BINARY, Alphabet.ALPHA_NUMERIC); // '1ly7vk'

baseConverter('1337', Alphabet.DECIMAL, Alphabet.BINARY); // '10100111001'
baseConverter('1337', Alphabet.DECIMAL, Alphabet.OCTAL); // '2471'
baseConverter('1337', Alphabet.DECIMAL, Alphabet.HEXA_DECIMAL); // '539'
baseConverter('1337', Alphabet.DECIMAL, Alphabet.ALPHA_LOWER); // 'bzl'
baseConverter('1337', Alphabet.DECIMAL, Alphabet.ALPHA); // 'zL'
baseConverter('1337', Alphabet.DECIMAL, Alphabet.ALPHA_NUMERIC); // 'lz'

baseConverter('CodeWars', Alphabet.ALPHA, Alphabet.BINARY); // '110100110111011111011110001100111111110000110'
baseConverter('CodeWars', Alphabet.ALPHA, Alphabet.OCTAL); // '646737361477606'
baseConverter('CodeWars', Alphabet.ALPHA, Alphabet.DECIMAL); // '29063972814726'
baseConverter('CodeWars', Alphabet.ALPHA, Alphabet.HEXA_DECIMAL); // '1a6efbc67f86'
baseConverter('CodeWars', Alphabet.ALPHA, Alphabet.ALPHA_LOWER); // 'fjepvaubis'
baseConverter('CodeWars', Alphabet.ALPHA, Alphabet.ALPHA_NUMERIC); // '8fGCU1me'

// ROT13 with custom alphabet
const customAlpha = 'nopqrstuvwxyzabcdefghijklmNOPQRSTUVWXYZABCDEFGHIJKLM';
baseConverter('PbqrJnef', Alphabet.ALPHA, customAlpha); // 'CodeWars'
baseConverter('chAllEnge', Alphabet.ALPHA, customAlpha); // 'puNyyRatr'

ArbitraryBaseConverter.markdown

Arbitrary Base Converter

Converts between arbitrary bases defined as alphabets (should work for any arbitrary alphabet not only for predefined ones):

const Alphabet = {
  BINARY:        '01',
  OCTAL:         '01234567',
  DECIMAL:       '0123456789',
  HEXA_DECIMAL:  '0123456789abcdef',
  ALPHA_LOWER:   'abcdefghijklmnopqrstuvwxyz',
  ALPHA_UPPER:   'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
  ALPHA:         'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ',
  ALPHA_NUMERIC: '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
};

Does not consider negative values.

A script by V.

License.