All 10 Functional Programming questions
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JavaScript › Functional Programming

What is function composition and how do you implement it?

Intermediate

Answer

Composition combines multiple small functions into one, where the output of each becomes the input to the next — typically implemented with a compose() or pipe() helper that reduces over an array of functions.
const pipe = (...fns) => (x) => fns.reduce((acc, fn) => fn(acc), x);
const addOne = n => n + 1;
const double = n => n * 2;
const transform = pipe(addOne, double);
transform(3); // (3+1)*2 = 8
Real-world example Building a data-processing pipeline that trims, validates, then formats user input in clearly separated steps.

Common follow-ups: What's the difference between pipe() and compose() in terms of execution order?

Destructuring Spread & Rest
All 10 Functional Programming questions