JavaScript Functions: Parameters and Return Values

A JavaScript function is a reusable block of code. Give it a clear name, pass information through parameters and return a result when needed.

Declare a function

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

const message = greet("Aadil");

Here, name is a parameter. Calling greet("Aadil") passes an argument, and the function returns a string.

Use an arrow function

const add = (first, second) => {
  return first + second;
};

const total = add(3, 4);

For a short expression, an arrow function can return the value directly:

const double = number => number * 2;

Keep functions focused

A function is easier to understand when it performs one clear job. Use meaningful names and return values rather than relying on unexpected changes elsewhere in the page.