Is there a way to learn what the type of something is at runtime, so that I can go back and fill in the type later?
TypeScript uses type erasure and does not run at runtime:
Closure, TypeScript and Dart, forgo soundness to deal with issues
of scale, code reuse, and popular programming patterns.
Use an alternative, such as the following:
typeof 1; /foo/ instanceof RegExp Error.isPrototypeOf(ReferenceError) this.constructor Object.getPrototypeOf(NaN)