Functions

Functions are reusable blocks of code that perform a specific task. They are one of the most important concepts in JavaScript — almost everything you build will be organised into functions.

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Function Declarations

The classic way to define a function:

function greet(name) {
  return "Hello, " + name + "!";
}

console.log(greet("Alice")); // "Hello, Alice!"

Key Characteristics

• Hoisted — you can call the function before its declaration in the code.
• The return statement sends a value back to the caller.
• If no return is specified, the function returns undefined.

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Function Expressions

A function assigned to a variable:

const greet = function(name) {
  return "Hello, " + name + "!";
};

console.log(greet("Bob")); // "Hello, Bob!"

Function expressions are not hoisted — you must define them before you use them.

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Arrow Functions

Introduced in ES6, arrow functions provide a shorter syntax:

// Standard arrow function
const greet = (name) => {
  return "Hello, " + name + "!";
};

// Concise body (implicit return for single expressions)
const double = (x) => x * 2;