hex2dec

hex2dec.js

const hex = process.argv[2];

const getInt = char =>
  ({
    A: '10',
    B: '11',
    C: '12',
    D: '13',
    E: '14',
    F: '15'
  }[char.toUpperCase()] || char);

const dec = hex
  .split('')
  .reverse()
  .reduce((acc, char, i) => {
    return acc + getInt(hex[i]) * Math.pow(16, hex.length - i - 1);
  }, 0);

console.log(dec);