As discussed below here is the solution similar to that in example but with if instead of while

const f = (_str, _k) => { let windowStart = 0; const maxArray = []; const charFrequency = {};

for (let windowEnd = 0; windowEnd < _str.length; windowEnd++) { const rightChar = _str[windowEnd]; maxArray.push(rightChar);

if (!(rightChar in charFrequency)) { charFrequency[rightChar] = 0; } charFrequency[rightChar] += 1;

if (Object.keys(charFrequency).length > _k) { maxArray.shift(); // removes the first element in the Array const leftChar = _str[windowStart]; charFrequency[leftChar] -= 1; if (charFrequency[leftChar] === 0) { delete charFrequency[leftChar]; } windowStart += 1; } } return maxArray.length; };