Online Node.js Compiler

const str = 'kjeljsdl'; const longestSubstring = (str = '') => { const { length } = str; if (length <= 1){ return 0; } const keys = [...new Set(str)]; const arr = []; let max = 0; for (let i = 0; i < keys.length - 1; i++) { for (let j = i + 1; j < keys.length; j++) { arr.push(keys[i] + keys[j]); } } arr.forEach(item => { let sub = ''; for (let i = 0; i < str.length; i++) { if (sub[sub.length - 1] === str[i]) { sub = ''; break; } if (item.includes(str[i])) { sub += str[i]; } } if (sub && sub.length > max){ max = sub.length; } }); return max; } console.log(longestSubstring(str));