Leetcode - 13. Roman to Integer

Explanation
The trick is IV is 4 because , I which is 1 is less than V which is 5

so we check in the iteration , that if next number is greater than current , then we need to take difference , else we can just add the value of Roman symbol

Javascript Code

/**
 * @param {string} s
 * @return {number}
 */
var romanToInt = function (s) {
    const RomanToIntmap = {
        "I": 1,
        "V": 5,
        "X": 10,
        "L": 50,
        "C": 100,
        "D": 500,
        "M": 1000
    }
    let res = 0;
    for (let i = 0; i < s.length; i++) {

        let curr = RomanToIntmap[s[i]];
        let next = RomanToIntmap[s[i + 1]];

        if (next > curr && next !== undefined) {
            res += next - curr;
            i++;
        }
        else {
            res += curr;
        }
    }
    return res
};