Most Common Word LeetCode solution in JavaScript

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// Memory Usage: 44.2 MB, less than 61.20%
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var mostCommonWord = function (paragraph, banned) {
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  paragraph = new Map(
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    Object.entries(
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      paragraph
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        .toLowerCase()
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        .match(/\b[a-z]+\b/gi)
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        .reduce((acc, cur) => ((acc[cur] = (acc[cur] || 0) + 1), acc), {})
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    ).sort((a, b) => b[1] - a[1])
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  );
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  for (let i = 0; i < banned.length; i++) paragraph.delete(banned[i]);
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  return paragraph.entries().next().value[0];
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};