Let's say we want to display three million, 3000000. This isn't that easy to read, you need to look closely to check that it isn't 300,000 or 30,000,000.
const number = 3000000; const numberToDisplay = new Intl.NumberFormat().format(number)
Bonus, it will be formatted according to the users' local settings. For me in Norway, numberToDisplay is 3 000 000. While 'en-US' it will be 3,000,000 and 'de-DE' it is 3.000.000