Mean of Array After Removing Some Elements LeetCode solution in JavaScript

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var trimMean = function (arr) {
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  arr.sort((a, b) => a - b);
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  let sum = 0;
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  for (let i = arr.length / 20; i < arr.length - arr.length / 20; i++) {
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    sum += arr[i];
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  }
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  return sum / (arr.length - arr.length / 10);
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};