How can I count the number of times different terms occur in a string string with JavaScript?

I have a list of 20 phrases that I want to count in an article.

Currently, I'm doing

      let counts = phrases.map((phrase, idx) => {
        phrase.usage = (articleBody.match(new RegExp(phrase.phrase, 'gi')) || []).length
        return phrase
      })

This requires me to do an expensive search each time. Is there some way to do it faster or all at once?

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