JavaScript Interview Question #176

What is functional programming in JavaScript?

Advanced JavaScript, Practical Problems & Senior Interview Scenarios Senior Advanced

Quick Interview Answer

Functional programming is a style of programming that emphasizes functions, expressions, immutability, composition, and minimizing shared mutable state. JavaScript supports this style because functions are first-class values and can be passed, returned, and composed.

Detailed Explanation

In practical JavaScript, functional techniques often appear in array transformations, pure utility functions, reducers, and data-processing pipelines. A production application does not need to be purely functional to benefit from these ideas.

Code Example

const products = [
    { name: "A", price: 100 },
    { name: "B", price: 200 }
];

const discounted = products
    .map(p => ({ ...p, price: p.price * 0.9 }))
    .filter(p => p.price >= 100);

console.log(discounted);