I use TypeScript because it's adoption by many developers, it's supported by many companies, and it's growth. AngularJS, React, @ASP.NET Core. I started using it in .NET Core, then for a job. Later I added more Angular experience and wrote more React software. It makes your code easier to understand and read... which means it makes other people's code easier to understand and read.
I use TypeScript because:
- incredible developer tooling and community support
- actively developed and supported by Microsoft (yes, I like Microsoft) ;)
- easier to make sense of a TS codebase because the annotations provide so much more context than plain JS
- refactors become easier (VSCode has superb support for TS)
I've switched back and forth between TS and Flow and decided a year ago to abandon Flow completely in favor of TS. I don't want to bash Flow, however, my main grievances are very poor tooling (editor integration leaves much to be desired), a slower release cycle, and subpar docs and community support.