Roman to Integer solution using TypeScript

Below is my TypeScript solution to the LeetCode "Roman to Integer" question.

Time Complexity: Because each character in the string will be visited only one time, and the string is of a limited length, the time complexity is O(1). If there were not a limit on the length of the string, the approach would have a time complexity of O(n).

Space Complexity: This approach will also use a constant amount of space, so the space complexity is O(1).

/**
 * Find the numerical value of a given string representing 
 * a Roman Numeral. For this exercise, Input is guaranteed 
 * to be within the range from 1 to 3999.
 *
 *   Time Complexity: O(1)
 *   Space Complexity: O(1)
 *
 *   Input: "MCMXCIV"
 *   Output: 1994
 *   Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
 */
function romanToInt(s: string): number {
    const map = new Map([
        ['I',  1],
        ['IV', 4],
        ['V',  5],
        ['IX', 9],
        ['X',  10],
        ['XL', 40],
        ['L',  50],
        ['XC', 90],
        ['C',  100],
        ['CD', 400],
        ['D',  500],
        ['CM', 900],
        ['M',  1000]
    ]);
    let result = 0;
    
    for(let i = 0; i < s.length; i++) {
        const twoSymbols = map.get(s[i] + s[i + 1]);
        const oneSymbol = map.get(s[i]);
        if (twoSymbols) {
            i += 1; // skip iteration of next symbol
        }
        result += twoSymbols || oneSymbol || 0;
    }
    
    return result;
};