Roman-to-Integer.js

/**
* @param {string} s
* @return {number}
*/
const romanToInt = s => {
  const chart = {
    I: 1,
    V: 5,
    X: 10,
    L: 50,
    C: 100,
    D: 500,
    M: 1000
  };
  let output = 0;
  [...s].forEach((value, index) => {
    const current = chart[s[index]];
    output += current < chart[s[index + 1]] || 0 ? -current : current;
  });
  return output;
};