roman_to_integer.js

var romanToInt = function (s) {
    // Map to store romans numerals
    const romanMap = new Map();
    // Fill the map
    romanMap.set('I', 1);
    romanMap.set('V', 5);
    romanMap.set('X', 10);
    romanMap.set('L', 50);
    romanMap.set('C', 100);
    romanMap.set('D', 500);
    romanMap.set('M', 1000);
    // Length of the given string
    const n = s.length;
    // Variable to store result
    let num = romanMap.get(s[n - 1]);
    // Loop for each character from right to left
    for (let i = n - 2; i >= 0; i--) {
        // Check if the character at right of current character is
        // bigger or smaller
        if (romanMap.get(s[i]) >= romanMap.get(s[i + 1])) {
            num += romanMap.get(s[i]);
        } else {
            num -= romanMap.get(s[i]);
        }
    }
    return num;
};


console.log(romanToInt("III"));
console.log(romanToInt("IV"));
console.log(romanToInt("IX"));
console.log(romanToInt("LVIII"));
console.log(romanToInt("MCMXCIV"));