Hacker News Reader

Does anyone know when TypeScript plans to introduce dynamic typing for function/method parameters? It would be very useful if TypeScript could infer the type of variables at runtime so that you never have to specify it.

View on HN

I may have missed your point, but wouldn’t this be essentially useless? You then have no type information about the parameters at all. Wouldn’t this just be the same as the existing implicit “any” type when not in strict mode?

I think it's a joke

Strongly typed functional languages (including Reason) can often figure out a function's parameter types based on how the variables are used in the function. For example, given `(a, b) => a.push(b * 2)`, it could figure out that `b` must be of type `number` and `a` must be of type `Array<number>`, so the function author wouldn't need to write the type annotations.

I think it's likely that TypeScript will never implement this (at least not at the level of sophistication of typical functional languages), given that it adds a lot of complexity to the language, and making types explicit at boundaries is usually good practice anyway.

It's arguable that they might, actually, add this in the future, but ... it would probably show up as part of how you can use TypeScript to type-check your JavaScript code such as when it infers types from JSDoc.

Reply on news.ycombinator.com