What are the methods to implement currying?

0-2 years experience

1. 1How would you write a simple curry helper that turns a binary function add(a, b) into addCurried(a)(b)?
2. 2If you call your curried function with only the first argument, what does it return and why?
3. 3What happens if you pass three arguments to a curried function that was designed for two?

2-5 years experience

1. 1We have a utility fetchData(url, options). How would you expose a curried version so developers can call fetchData(url)(options) while still supporting the original two‑argument call?
2. 2During a code review you notice a curried function leaking memory because it closes over a large object. How would you diagnose and fix the leak?
3. 3Why might a naive curry implementation break when the original function uses default parameters or rest parameters?

5-8 years experience

1. 1Our front‑end framework relies heavily on curried functions, but we see performance degradation from repeatedly creating wrapper functions. How would you redesign the currying utility to reduce overhead while keeping the API ergonomic?
2. 2We need a public API that supports both curried and uncurried invocation across multiple services. What design patterns would you use to keep TypeScript type safety and avoid duplicated code?
3. 3How would you benchmark different currying implementations (manual closure, bind, arrow functions) to choose the best approach for a high‑traffic single‑page application?

8+ years experience

1. 1Our legacy codebase uses manual partial application. What migration strategy would you propose to replace it with a standardized curried utility while minimizing risk across teams?
2. 2When designing a shared internal library, how would you decide whether to enforce currying as a convention, considering cross‑language interoperability and long‑term maintainability?
3. 3What are the trade‑offs between implementing currying at runtime versus generating pre‑curried functions at build time with a code transformer, and how would you guide teams in adopting the chosen approach?