Maximum Number of Vowels in a Substring of Given Length LeetCode solution in JavaScript

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var maxVowels = function (s, k) {
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  let vowels = ["a", "e", "i", "o", "u"];
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  let maxCount = 0;
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  let start = 0; // the left edge of the window
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  let count = 0; // count of vowels for current substring
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  // expanding the right edge of the window one character at a time
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  for (let end = 0; end < s.length; end++) {
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    // increment count of vowels for current substring if the current character is present in vowels array
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    if (vowels.includes(s[end])) {
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      count += 1;
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    }
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    // if substring is longer than K, let's shrink the window by moving left edge
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    if (end - start + 1 > k) {
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      // reduce the current count by one if the character on the left edge is vowel
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      if (vowels.includes(s[start])) {
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        count -= 1;
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      }
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      //shrinking the left edge of the window
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      start += 1;
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    }
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    // checking if current count is larger than current maximum count
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    maxCount = Math.max(maxCount, count);
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    // if maxCount is equal to K, no need to check further, it is the max possible count
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    if (maxCount == k) return maxCount;
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  }
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  return maxCount;
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};