Maximum Twin Sum of a Linked List LeetCode solution in JavaScript

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var pairSum = function (head) {
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  const arr = [];
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  let max = 0;
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  while (head) {
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    arr.push(head.val);
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    head = head.next;
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  }
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  for (let i = 0; i < arr.length / 2; i++) {
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    const sum = arr[i] + arr[arr.length - 1 - i];
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    max = Math.max(max, sum);
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  }
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  return max;
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};