SOURCE

var romanToInt = function(s) {
    let nums = []
    for(let i = 0; i < s.length; i++){
        let num = 0
        switch(s[i]){
            case 'M':
                num = 1000
                break;
            case 'D':
             num = 500
                break;
            case 'C':
             num = 100
                break;
            case 'L':
             num = 50
                break;
            case 'X':
             num = 10
                break;
            case 'V':
             num = 5
                break;
            case 'I':
             num = 1
                break;
        }
        nums[i] = num
    }
    let count = 0
    for(let i = 0; i < nums.length; i++){
        if(nums[i] < nums[i + 1] && i + 1 < nums.length - 1){
            nums[i] = -nums[i]
        }
        count += nums[i]
    }
    return count

};

console.log(romanToInt("MCMXCIV"))