Contains Duplicate LeetCode solution in JavaScript

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var containsDuplicate = function (nums) {
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  if (nums.length <= 1) return false;
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  let cache = {};
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  let mid = Math.floor(nums.length / 2);
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  let left = mid - 1;
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  let right = mid;
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  while (left >= 0 || right < nums.length) {
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    if (nums[left] === nums[right]) {
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      return true;
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    }
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    if (cache[nums[left]]) {
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      return true;
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    } else {
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      cache[nums[left]] = true;
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    }
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    if (cache[nums[right]]) {
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      return true;
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    } else {
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      cache[nums[right]] = true;
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    }
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    left--;
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    right++;
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  }
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  return false;
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};