JavaScript Functions - Exercise 1

A function is a reusable block of code that performs a specific task. Functions can take inputs called parameters, run some logic, and optionally return a value. In JavaScript, you can create them with the function keyword or with arrow-function syntax.

function greet(name) {
  return `Hello, ${name}!`;
}
console.log(greet("World")); // Hello, World!

A function declaration gives a function a name and defines the code it runs. Call it by writing its name followed by parentheses.

function greet() {
  console.log("Hello!");
}
greet();

Parameters are the named inputs in a function definition. Arguments are the values passed to the function when it is called.

function greet(name) {
  return `Hello, ${name}!`;
}
console.log(greet("Ada"));

return sends a value back to the code that called the function and immediately ends that function's execution.

function add(left, right) {
  return left + right;
}
const total = add(2, 3);
console.log(total);

An arrow function is a shorter function syntax that uses =>. For a single expression, it returns the expression implicitly.

const square = number => number * number;
console.log(square(4));

A default parameter provides a value when the caller omits an argument or passes undefined.

function greet(name = "friend") {
  return `Hello, ${name}!`;
}
console.log(greet());

A callback is a function passed to another function so it can be called later.

function runTask(task) {
  return task();
}
console.log(runTask(() => "Complete"));

Variables declared with let or const inside a function are available only within that function.

function showMessage() {
  const message = "Inside the function";
  console.log(message);
}
showMessage();

Yes. JavaScript functions are values, so you can assign them to variables and call them through those variables.

const sayHello = function () {
  return "Hello!";
};
console.log(sayHello());

Function declarations are hoisted, so they can be called before their declaration appears in the source code.

sayHello();
function sayHello() {
  console.log("Hello!");
}