Minimum Lines to Represent a Line Chart LeetCode solution in JavaScript

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var minimumLines = function (stockPrices) {
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  if (stockPrices.length <= 1) return 0;
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  stockPrices.sort((a, b) => a[0] - b[0]);
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  var dates = stockPrices.map((el) => el[0]);
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  var price = stockPrices.map((el) => el[1]);
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  var count = 0;
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  for (var i = 0; i < dates.length - 2; i++) {
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    var area1 =
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      BigInt(price[i + 1] - price[i]) * BigInt(dates[i + 2] - dates[i + 1]);
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    var area2 =
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      BigInt(dates[i + 1] - dates[i]) * BigInt(price[i + 2] - price[i + 1]);
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    if (area1 !== area2) {
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      count++;
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    }
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  }
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  return count + 1;
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};