A function is a named, reusable block of code that performs a task. Instead of copying the same steps everywhere you need them, you write them once as a function and call it by name whenever you need it.
function greet(name) {
console.log("Hello, " + name + "!");
}
greet("Ada"); // "Hello, Ada!"
greet("Alan"); // "Hello, Alan!"name here is called a parameter — a placeholder for the value the function will receive each time it's called.
A function can hand a value back to whatever called it, using return.
function add(a, b) {
return a + b;
}
let result = add(3, 4);
console.log(result); // 7Functions make code reusable, easier to test in isolation, and easier to read — a well-named function like calculateTotalPrice() tells you what a block of code does without needing to read every line inside it.