Minimum Number of Operations to Move All Balls to Each Box LeetCode solution in JavaScript

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var minOperations = function (boxes) {
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  const ans = new Array(boxes.length).fill(0);
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  let ballsLeft = 0,
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    ballsRight = 0;
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  let movesLeft = 0,
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    movesRight = 0;
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  const len = boxes.length - 1;
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  for (let i = 0; i <= len; i++) {
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    movesLeft += ballsLeft;
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    movesRight += ballsRight;
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    ans[i] += movesLeft;
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    ans[len - i] += movesRight;
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    ballsLeft += +boxes[i];
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    ballsRight += +boxes[len - i];
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  }
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  return ans;
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};