For developing a working metronome in JS, I relied heavily on this article by Grant James. He goes in depth into the issues associated with timing in JavaScript and how to utilize the Web Audio API to keep accurate time and setInterval() to periodically check for user-initiated changes in tempo.
Additionally, I've integrated the Metronome class from his repo. To begin, I copied his code into this project to get a bare bones metronome working. The original project is written in JavaScript, so I have added typings to the Metronome class for use in TypeScript.