JavaScript Advanced Day 1: Advanced Functions & Patterns

Goal of this Day

Today you will learn:

• How to master advanced functions in JavaScript
• Higher-order functions
• Currying and partial application
• IIFE (Immediately Invoked Function Expression)
• Function composition

By the end, you will write cleaner, reusable, and more powerful functions.

Step 1: Higher-Order Functions

A function that takes another function as argument or returns a function.

const add = x => y => x + y;
console.log(add(2)(3)); // 5

Step 2: IIFE

Immediately Invoked Function Expression runs immediately:

(function(){
  console.log("IIFE runs immediately!");
})();

Step 3: Currying & Partial Application

Transform a function with multiple arguments into a sequence of functions:

const multiply = x => y => x * y;
console.log(multiply(2)(3)); // 6

Step 4: Function Composition

Combine multiple functions to produce a new function:

const compose = (f, g) => x => f(g(x));

const double = x => x * 2;
const square = x => x * x;

console.log(compose(square, double)(3)); // 36

Practice

const add = x => y => x + y;
console.log(add(2)(3));

(function(){
  console.log("IIFE runs immediately!");
})();

Task

Complete the following:

• Create a curried function that multiplies two numbers
• Write an IIFE that prints your name

Example:

// Curried multiplication function
const multiply = x => y => x * y;
console.log(multiply(4)(5)); // 20

// IIFE printing name
(function(){
  console.log("Alex");
})();