🔍 What is Currying?
Currying is a functional programming technique where a function with multiple arguments is transformed into a sequence of functions, each taking one argument at a time.
Instead of:
const add = (a, b) => a + b; You curry it as:
const curriedAdd = (a) => (b) => a + b; 📌 Why Use Currying?
- Reusability: You can create specialized versions of functions.
- Function composition: Useful in pipelines and functional chains.
- Cleaner syntax for functional operations.
✅ Examples
1. Normal Function
const add = (a, b) => a + b; console.log(add(2, 3)); // 5 2. Curried Function
const curriedAdd = (a) => (b) => a + b; console.log(curriedAdd(3)(5)); // 8 3. Multi-level Curried Function
function curriedAdd2(a) { return function (b) { return function (c) { return a + b + c; }; }; } console.log(curriedAdd2(4)(6)(2)); // 12 4. Real-Life Example: Calculating Discount
Normal:
const totalPrice = (amount, discount) => amount - amount * discount; console.log(totalPrice(100, 0.3)); // 70 Curried:
const curriedTotalPrice = (discount) => (amount) => amount - amount * discount; const withDiscount = curriedTotalPrice(0.3); console.log(withDiscount(100)); // 70 console.log(withDiscount(200)); // 140 console.log(withDiscount(250)); // 175 This helps you reuse the same discount logic without repeating the discount value every time.
🛠 Currying in Redux Middleware
Redux middleware often uses currying to handle the flow of store → next → action.
const logger = (store) => (next) => (action) => { console.group(action.type); console.info("previous state", store.getState()); const result = next(action); console.info("next state", store.getState()); console.groupEnd(); return result; }; export default logger; This is a triple-curried function:
-
(store)gives access to the state and dispatch -
(next)passes control to the next middleware or reducer -
(action)is the actual dispatched action
Used in store.ts like this:
import logger from "./middlewares/logger"; middleware: (getDefaultMiddleware) => getDefaultMiddleware().concat(logger); 🧩 Summary
| Concept | Explanation |
|---|---|
| Currying | Transforming a function so it takes arguments one at a time |
| Syntax | f(a, b) → f(a)(b) |
| Use Case | Reusability, configuration, partial application |
| Redux | Currying is used in middleware to access store, next, and action |
--this article is written with the help of AI.
Top comments (0)