Minimum Increment to Make Array Unique LeetCode solution in JavaScript

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var minIncrementForUnique = function (nums) {
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  let ans = 0,
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    arr = nums.sort((a, b) => a - b);
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  for (let i = 0; i < arr.length; i++) {
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    if (arr[i] === arr[i + 1]) {
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      arr[i + 1]++;
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      ans++;
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    } else if (arr[i] > arr[i + 1]) {
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      if (arr[i] - arr[i - 1] === 1) {
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        ans += arr[i] - arr[i + 1] + 1;
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        arr[i + 1] += arr[i] - arr[i + 1] + 1;
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      }
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    }
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  }
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  return ans;
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};