Count Common Words With One Occurrence LeetCode solution in JavaScript

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var countWords = function (words1, words2) {
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  const map1 = new Map();
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  const map2 = new Map();
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  let count = 0;
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  for (const word of words1) {
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    map1.set(word, map1.get(word) + 1 || 1);
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  }
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  for (const word of words2) {
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    map2.set(word, map2.get(word) + 1 || 1);
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  }
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  for (const word of words1) {
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    if (map1.get(word) === 1 && map2.get(word) === 1) count++;
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  }
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  return count;
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};