Implement Currying using ES6 Arrow Functions

0-2 years experience

1. 1How would you write a curried add function using ES6 arrow syntax so it can be called like add(2)(3)?
2. 2If you invoke your curried function with the first argument and later with the second, what value is returned each time?

2-5 years experience

1. 1We have a utility `fetchData(url, options)` and want to support partial application. How would you refactor it to be curried, and what trade‑offs might that introduce?
2. 2During a code review you see a curried function returning undefined when called as fn(a, b). How would you debug the issue and correct the implementation?

5-8 years experience

1. 1Our front‑end team wants a curried API for configuring UI components, but most of the codebase uses regular functions. How would you design a wrapper that supports both styles without hurting performance?
2. 2When using curried functions to pre‑configure server‑side rendering options, what are the memory and call‑stack implications, and how would you mitigate any problems?

8+ years experience

1. 1A legacy monolith is being split into micro‑frontends. How would you decide whether to keep existing curried helpers or replace them with plain functions, and how would you plan the migration to avoid breaking contracts across teams?
2. 2Your organization is standardizing a shared functional utilities library. What guidelines would you set for exposing functions as curried versus non‑curried, considering readability, tree‑shaking, and TypeScript typings?