Sliding window in TypeScript

sw.ts

// Find the longest length of a substring without repeating characters, e.g. "abcabc" => 3
function lengthOfLongestSubstring(s: string): number {
    let n = s.length;
    let longest = 0;
    let nextIndex = [];
    
    for (let right = 0, left = 0; right < n; right++) {
        left = Math.max(nextIndex[s.charAt(right)] || 0, left);
        longest = Math.max(longest, right - left + 1);
        nextIndex[s.charAt(right)] = right + 1;
    }
    
    return longest;
};