The length read-only property of the SpeechRecognitionResultList interface returns the length of the "array" — the number of SpeechRecognitionResult objects in the list.
A number.
This code is excerpted from our Speech color changer example.
recognition.onresult = (event) => {
const color = event.results[0][0].transcript;
diagnostic.textContent = `Result received: ${color}.`;
bg.style.backgroundColor = color;
console.log(event.results.length);
};