Closest Subsequence Sum LeetCode solution in JavaScript

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var minAbsDifference = function (nums, goal) {
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  let mid = Math.floor(nums.length / 2);
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  let part1 = nums.slice(0, mid),
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    part2 = nums.slice(mid);
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  function findSubsetSums(arr, set, idx = 0, sum = 0) {
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    if (idx === arr.length) return set.add(sum);
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    findSubsetSums(arr, set, idx + 1, sum);
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    findSubsetSums(arr, set, idx + 1, sum + arr[idx]);
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  }
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  let sum1 = new Set(),
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    sum2 = new Set();
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  findSubsetSums(part1, sum1);
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  findSubsetSums(part2, sum2);
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  sum1 = [...sum1.values()];
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  sum2 = [...sum2.values()];
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  sum2.sort((a, b) => a - b);
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  let min = Infinity;
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  for (let num1 of sum1) {
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    let l = 0,
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      r = sum2.length - 1;
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    while (l <= r) {
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      let mid = l + Math.floor((r - l) / 2);
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      let num2 = sum2[mid];
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      min = Math.min(min, Math.abs(num1 + num2 - goal));
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      if (num1 + num2 < goal) l = mid + 1;
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      else r = mid - 1;
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    }
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  }
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  return min;
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};