How to count number of "words" in Chinese/Japanese content in Javascript

I'm trying to write a method to count the number of words when the content is in chinese and japanese. This should exclude the special characters / punctuations / whiteSpaces.

I tried creating a regex for each locale and find the words based on it. Tried looking for existing regex on internet but none of them seems to be working. My approach -

function countWords(text, locale) {
  let wordCount = 0;
  
  // Set the word boundary based on the locale
  let wordBoundary = '\\b';
  
  if (locale === 'ja') {
    // Japanese word boundary
    wordBoundary = '[\\p{Script=Hiragana}\\p{Script=Katakana}\\p{Script=Han}ー]+';
  } else if (locale === 'zh') {
    // Chinese word boundary
    wordBoundary = '[\\p{Script=Han}]+';
  }
  
  const regex = new RegExp(wordBoundary, 'gu');
  const matches = text.matchAll(regex);
  
  for (const match of matches) {
    wordCount++;
  }
  
  return wordCount;
}

I thought this should work, but I'm comparing the word count in MS word and using this logic, they are coming different

A possible word count approach could be based on a text segmentation array which was the result of calling an Intl.Segmenter instance's segment method.

Each segmented item features properties like e.g. ...

{ segment: 'words', index: 9, input: 'How many words ...', isWordLike: true }

... thus, in order to get the total word count, one could reduce the array of text segment items by validating an item's isWordLike value ...

function countWords(text, locale) {
  return [
    ...new Intl.Segmenter(locale, { granularity: 'word' })
      .segment(text)
  ]
  .reduce((wordCount, { isWordLike }) =>
    wordCount + Number(isWordLike), 0
  );
}

console.log(
  "countWords('How many words does the text contain?', 'en') ?..",
  countWords('How many words does the text contain?', 'en'),
);
console.log(
  "countWords('Combien de mots contient ce texte ?', 'fr') ?..",
  countWords('Combien de mots contient ce texte ?', 'fr'),
);

console.log(
  "countWords('そのテキストには何語含まれていますか？', 'ja') ?..",
  countWords('そのテキストには何語含まれていますか？', 'ja'),
);
console.log(
  "countWords('该文本包含多少个单词？', 'zh') ?..",
  countWords('该文本包含多少个单词？', 'zh'),
);

.as-console-wrapper { min-height: 100%!important; top: 0; }

Note ... as of now Firefox still does not support/implement Intl.Segmenter