base conversion functions

base_conversion.js

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

function convert(input, source, target) {
  return fromNum(toNum(input, source), target);
}

function toNum(inp, str) {
  return inp.split('').reduce((r, c, i) => {
    let idx = str.indexOf(c);
    return r + Math.pow(str.length, inp.length-i-1) * idx;
  }, 0);
}

function fromNum(inp, str) {
  let res = [];
  let base = str.length;
  while (inp) {
    let tmp = inp % base;
    res.unshift(str[tmp]);
    inp = (inp - tmp) / base;
  }
  return res.join('') || str[0];
}