Exclusive Time of Functions LeetCode solution in JavaScript

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var exclusiveTime = function (n, logs) {
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  const stack = [];
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  let preTimeStamp = 0;
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  return logs.reduce((times, log) => {
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    const [id, status, timeStamp] = log.split(":");
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    const time = +timeStamp - preTimeStamp;
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    const { length } = stack;
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    if (length) {
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      const lastId = stack[length - 1];
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      times[lastId] += time;
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    }
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    preTimeStamp = +timeStamp;
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    if (status === "start") stack.push(id);
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    else {
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      const lastId = stack.pop();
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      times[lastId] += 1;
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      preTimeStamp += 1;
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    }
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    return times;
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  }, Array(n).fill(0));
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};