Learn Parameters and Return Values

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When you call a function like calculateRectangleArea, you provide values known as arguments. These arguments are passed to the function's parameters, in this case, width and height.


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function calculateRectangleArea(width, height) {
  return width * height;
}

const area = calculateRectangleArea(5, 3);
console.log("The area of the rectangle is:", area);

Inside the function, you can use these parameters as variables. When the function completes its calculation, it uses the return keyword to send a value back to where it was called. Here, width * height is returned, so when you call calculateRectangleArea(5, 3), the function returns 15, which is then stored in the area variable. The console.log statement prints this result for you to see.

Note

A function can only return one value at a time, and as soon as it reaches a return statement, it stops running and exits immediately. If you do not use return, the function returns undefined by default.

Functions can also have default parameters, which are values that are used if no argument is provided for a parameter. This makes your functions more flexible and prevents errors if a value is missing. You can also use return early in a function if a certain condition is met and you want to exit before reaching the end.

For example, you could write a function like this:


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function greet(name = "Guest") {
  if (!name) {
    return "No name provided.";
  }
  return "Hello, " + name + "!";
}

console.log(greet());
console.log(greet(""));
console.log(greet("Alice"));

If you call greet() with no argument, it uses the default "Guest". If you call greet(""), the function returns early with "No name provided.". This approach helps you handle different scenarios and makes your code easier to maintain.

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Section 1. Chapter 10

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Section 1. Chapter 10