Historically, virtually every move up the abstraction level sacrificed performance to gain programming efficiency. Assembly to C, C to C++, C++ to Java, Java to Python/Javascript. And now there are wars over Javascript vs. Typescript, and jQuery vs. React/Angular. Every new step up the stack claims that the higher level of abstraction can either be implemented with only a minimal penalty, or could actually improve performance due to easier automated optimization. However, every time, it seems that in practical applications, performance is sacrificed to make software development faster.
I don't know enough about the performance of Javascript vs. Typescript to form a strong opinion about it, but if history is any guide, it's likely that it improves software development efficiency at the expense of performance.
Typescript usually transpiles to javascript, just without the type information, and this is not done in the browser. If you target old browsers it can add maybe add some overhead like babel does.
I don't know about javascript's usual JIT compilers, but LuaJIT's JIT compiler (trace compiler) does a pretty good job of figuring out abstractions.
I mean, JavaScript comes out 4.5x slower and consuming 6.5x more memory. For TypeScript the numbers are 22x and 46x respectively. That honestly makes me very suspicious about the benchmark set-up.
I don't know enough about the performance of Javascript vs. Typescript to form a strong opinion about it, but if history is any guide, it's likely that it improves software development efficiency at the expense of performance.