> Can’t this be accomplished with JavaScript? Assuming your interested in clean code and best practices.

There's nothing that prevents you from swimming against a stream, but we know swimming with the stream is faster. Same thing here. It's not impossible in javascript, but typescript makes code maintenance much more easier.

> Can’t you also write unit tests in JavaScript?

"Being more than sum of its parts" and all that.

> This is a false sense of security. “Compiling” without errors just tells me I did not do something dumb like assign a string to an int. Is this really the main issue devs have? From what I have seen no… Devs usually need to chase down and understand the code regardless of type checking.

Typescript does not solve all the software engineering problems. It makes common problems and annoyances much more easy to handle.