How to create and use higher-order functions in JavaScript

Short answer

Higher-order functions accept other functions as arguments or return functions, enabling abstraction over behavior, callbacks, and functional composition.

Steps

1. Accept a function as a callback: javascript function mapArray(arr, transform) { const result = []; for (const item of arr) result.push(transform(item)); return result; } console.log(mapArray([1, 2, 3], x => x * 2)); // [2, 4, 6]
2. Return a function to create specialized behavior: javascript function greaterThan(n) { return m => m > n; } const greaterThan10 = greaterThan(10); console.log(greaterThan10(11)); // true
3. Compose functions for reusable pipelines: javascript const compose = (...fns) => x => fns.reduceRight((v, f) => f(v), x); const add1 = x => x + 1; const double = x => x * 2; console.log(compose(double, add1)(3)); // 8

Tips

• Higher-order functions reduce repetition by abstracting control flow.
• Keep returned functions pure when possible for easier testing.

Common issues

• Over-nesting higher-order functions can hurt readability; name intermediate steps.
• Forgetting to handle this context when passing methods as callbacks.