Thank you. I wouldn’t say TypeScript is strictly needed, it’s is just another tool in the development toolbox to help catch bugs.

Probably for small project/team size it is overkill, but once either a project or team gets large enough then comes into its own.

For example, Reddit use TypeScript and they detail why compared to others such as Flow in this blog post: https://redditblog.com/2017/06/30/why-we-chose-typescript/