Corporate Flight Bookings LeetCode solution in JavaScript

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var corpFlightBookings = function (bookings, n) {
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  // +1 as dummy guard on the tail, which allow us not to check right boundary every time
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  let unitStep = Array(n + 1).fill(0);
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  for (const [first, last, seatVector] of bookings) {
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    // -1 because booking flight is 1-indexed, given by description
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    let [left, right] = [first - 1, last - 1];
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    unitStep[left] += seatVector;
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    unitStep[right + 1] -= seatVector;
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  }
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  // Reconstruct booking as drawing combination of retangle signal, built with unit step impulse
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  for (let i = 1; i < unitStep.length; i++) {
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    unitStep[i] += unitStep[i - 1];
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  }
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  // last one is dummy guard on the tail, no need to return
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  return unitStep.slice(0, n);
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};