Higher Order Functions

_Higher-Order-Functions.md

Higher Order Functions

Higher Order Functions (HOF) take one or more functions as arguments and they must be trigger in the first order. They often return function as the output.

When I use HOF?

• Defining callbacks
• Composition
• map / reduce

Before going forward please read about Composition.

example1.js

const array = [1,2,3,4,5,6,7,8,9];

// filter is higher order function as it takes a function as a param
const evenNums = array.filter(num => num % 2 === 0);
console.log('even numbers in array: ', ...evenNums);

// higher order functions often return other functions.
function calculate (f) {
    return function (a, b) {
        return f(a, b);
    }
}
// function composition :)
const sum = calculate((a, b) => a + b);
console.log('sum: ', sum(1, 2));