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

roman-to-integer.js

/**
 * @param {string} s
 * @return {number}
 */
var romanToInt = function(s) {
    const symbols = {
        "I": 1,
        "V": 5,
        "X": 10,
        "L": 50,
        "C": 100,
        "D": 500,
        "M": 1000
    }
    let acc = 0
    while (s.length>0) {
        if (symbols[s[1]] > symbols[s[0]]) {
            acc += symbols[s[1]] - symbols[s[0]]
            s = s.substr(2,)
        } else {
            acc += symbols[s[0]]
            s = s.substr(1,)
        }
    }
    return acc
};

3+4 is equal to 3-1+5. I just didn't think about it