Hand of Straights LeetCode solution in JavaScript

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var isNStraightHand = function (hand, groupSize) {
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  if (hand.length % groupSize !== 0) return false;
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  const map = new Map();
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  hand.forEach((h) => {
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    map.set(h, map.get(h) + 1 || 1);
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  });
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  // sort based on the key in asc order
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  const sortedMap = new Map([...map.entries()].sort((a, b) => a[0] - b[0]));
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  while (sortedMap.size) {
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    // getting the first key
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    const firstKey = sortedMap.keys().next().value;
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    for (let i = firstKey; i < firstKey + groupSize; ++i) {
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      if (!sortedMap.has(i)) {
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        return false;
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      }
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      const freq = sortedMap.get(i);
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      if (freq === 1) {
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        sortedMap.delete(i);
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      } else {
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        sortedMap.set(i, sortedMap.get(i) - 1);
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      }
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    }
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  }
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  return true;
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};