Currying Implementation and Examples

Currying Implementation and Examples

Manual Currying

function multiply(a) {
  return function (b) {
    return function (c) {
      return a * b * c;
    };
  };
}
multiply(2)(3)(4); // 24

Generic curry

function curry(fn) {
  return function curried(...args) {
    if (args.length >= fn.length) return fn(...args);
    return (...next) => curried(...args, ...next);
  };
}

Practical Example: Logging

const log = curry((level, timestamp, message) => {
  console.log(`[${level}] [${timestamp}] ${message}`);
});
const error = log("ERROR");
const errorNow = error(new Date().toISOString());
errorNow("Something broke");

Practical Example: Filtering

const filter = curry((predicate, arr) => arr.filter(predicate));
const isEven = (n) => n % 2 === 0;
const filterEven = filter(isEven);
filterEven([1, 2, 3, 4]); // [2, 4]

The Takeaway

Currying: manually (nested functions) or generically (recursive curry function). Practical uses: logging (preset level, timestamp), filtering (preset predicate), and any configurable function. Each partial call returns a new function that closes over the accumulated arguments.