TypeScript's satisfies Operator, Explained With Real Code

For a long time I reached for type annotations everywhere. Then I kept losing autocomplete on my config objects, and satisfies turned out to be the fix.

The problem with annotations

Annotating a value with a broad type makes TypeScript forget the specific keys you actually wrote. You get safety, but you lose precision.

satisfies keeps both

With satisfies, the object is still checked against Routes, but its own type stays exactly what you wrote.