What is a higher order function

A higher-order function is a function that takes another function as an argument or returns a function.

Example 1: Takes a function as an argument

function greet(name) {
  return `Hello, ${name}`;
}

function processUser(callback) {
  console.log(callback("John"));
}

processUser(greet);

Output:

Hello, John

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Example 2: Returns a function

function multiply(x) {
  return function (y) {
    return x * y;
  };
}

const double = multiply(2);
console.log(double(5)); // 10

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Common Higher-Order Functions in JavaScript

• map()
• filter()
• reduce()
• forEach()
• find()
• setTimeout()

Example:

const numbers = [1, 2, 3];

const doubled = numbers.map(num => num * 2);

Here, map() is a higher-order function because it takes a callback function.