0013.js

var romanToInt = function (s) {
  let sum = 0;

  for (let i = 0; i <= s.length; i++) {
    switch (s[i]) {//checks wether s contains any value
      case 'I':
        if (s[i + 1] === "V") {
          sum += 4;
        }
        else if (s[i + 1] === "X") {
          continue;
        }
        else {
          sum += 1;
        }
        break;
      case 'V':
        if (s[i - 1] === "I") {
          continue;
        }
        else {
          sum += 5;
        }
        break;
      case 'X':
        if (s[i - 1] === "I") {
          sum += 9;
        }
        else if (s[i + 1] === "L") {
          sum += 40;
        }
        else if (s[i + 1] === "C") {
          sum += 90;
        }
        else {
          sum += 10;
        }
        break;
      case 'L':
        if (s[i - 1] === "X") {
          continue;
        }
        else { sum += 50; }

        break;
      case 'C':
        if (s[i + 1] === "M") {
          sum += 900;
        }
        else if (s[i + 1] === "D") {
          sum += 400;
        }
        else if (s[i - 1] === "X") {
          continue;
        }
        else {
          sum += 100;
        }
        break;
      case 'D':
        if (s[i - 1] === "C") {
          continue;
        }
        sum += 500;
        break;
      case 'M':
        if (s[i - 1] === "C") {
          continue;
        }
        else {
          sum += 1000;
        }
        break;
    }
  }
  return sum;

};