Ranked in these QuestionsQuestion Ranking
Pro Checks to see if you check for Nulls
Because getting those exceptions is just not fun and very pervasive.
Pro There is support in many code editors via the extension
For example, there is good support through the extension in Visual Studio Code, which is a good editor for TypeScript, which is a competitor to Flow.
Pro Versioned type definitions
Pro Babel extension for strip of type annotations
Thanks to the Babel extension for the output, there is minimally modified code that is understandable to the author.
For example, there are definitions for Gulp, React.