What are the methods to implement currying?

We can curry a function either manually, using recursion, bind method, reduce method or lodash utility

Difficulty: 5/10

Topics: currying techniques, higher-order functions, function arity

0-2 years experience

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

2-5 years experience

1
We 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
During 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
Why might a naive curry implementation break when the original function uses default parameters or rest parameters?

5-8 years experience

1
Our 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
We 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
How 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
Our 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
When 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
What 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?

❓Can you walk me through the closure that your curry function creates?
❓How does your implementation preserve the original function's `this` binding?
❓What are the performance implications of using `Function.prototype.bind` versus a manual closure?