13. Roman to Integer

https://leetcode.com/problems/roman-to-integer/

I parsed Roman ex)IXIV to Integer ex)94 in this problem.

let alphas = ["I", "V", "X", "L", "C", "D", "M", "", ""];
/**
 * @param {string} s
 * @return {number}
 */
var romanToInt = function (s) {
  let sum = 0;
  for (let i = 0; i < s.length; i++) {
    let c = s[i];
    let ci = alphas.findIndex((a) => a === c);
    if (ci % 2) {
      sum += 5 * Math.pow(10, (ci - 1) / 2);
      continue;
    }
    let tens = Math.pow(10, ci / 2);
    let nc = s[i + 1];
    if (nc === alphas[ci + 1]) {
      sum += 4 * tens;
      i++;
      continue;
    }
    if (nc === alphas[ci + 2]) {
      sum += 9 * tens;
      i++;
      continue;
    }
    if (nc === c) {
      if (s[i + 2] === c) {
        sum += 3 * tens;
        i += 2;
        continue;
      }
      sum += 2 * tens;
      i++;
      continue;
    }
    sum += tens;
  }
  return sum;
};