With Flow you can also add types gradually. Actually, one of the reasons why Facebook created Flow is that they thought that TypeScript was not "gradual enough"

With Flow you can also add types gradually. Actually, one of the reasons why Facebook created Flow is that they thought that TypeScript was not "gradual enough". A good presentation on how Flow differs from other type systems: https://www.youtube.com/watch?v=VEaDsKyDxkY https://www.youtube.com/watch?v=VEaDsKyDxkY