JavaScript Functions

Functions are reusable blocks of code. Define once, call anywhere.

Declaring a function

A function declaration names a block you can run later.

function greet(name) {
  console.log("Hello, " + name);
}

greet("Ada");
greet("Grace");

Parameters are the inputs a function expects. Arguments are the values you pass in.

function add(a, b) {
  return a + b;
}

const total = add(3, 4);
console.log(total);

return sends a value back to the caller. Without it, a function returns undefined.

function square(n) {
  return n * n;
}

console.log(square(5));

Arrow functions are a shorter syntax, common in modern JavaScript.

const double = (n) => n * 2;

console.log(double(21));