Longest Subarray of 1's After Deleting One Element LeetCode solution in JavaScript

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var longestSubarray = function (nums) {
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  let l = 0,
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    r = 0;
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  let longest = 0;
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  // Keep track of the idx where the last zero was seen
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  let zeroIdx = null;
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  while (r < nums.length) {
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    // If we encounter a zero
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    if (nums[r] === 0) {
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      // If this is the first zero encountered, then set the zeroIdx to the current r index
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      if (zeroIdx === null) zeroIdx = r;
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      else {
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        // If we've already encountered a zero, then set the l index to the zeroIdx + 1,
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        // effectively removing that zero from the subarray
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        l = zeroIdx + 1;
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        // Then update the zeroIdx to the current r index
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        // This way there will be, at most, one zero in the subarray at all times
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        zeroIdx = r;
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      }
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    }
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    longest = Math.max(longest, r - l);
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    r++;
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  }
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  return longest;
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};