What Is Functional Programming

Short answer

Functional Programming treats computation as the evaluation of mathematical functions. It avoids mutable state and side effects.

How it works

• Pure functions: Output depends only on input, with no side effects.
• Immutability: Data is never modified; new data is created instead.
• Higher-order functions: Functions can accept and return other functions.

Example

const doubled = [1, 2, 3].map(x => x * 2);

map is a higher-order function that produces a new array without mutating the original.

Why it matters

FP simplifies concurrency because immutable data eliminates race conditions. It also makes code easier to test and reason about.