Return values
Up to this point, the functions you've built have output to the console. This output can be exactly what you're looking for, especially when you create functions that call other services. But what if you want to create a helper function to perform a calculation and then provide a value that you can use elsewhere?
You can create this function by using a return value. A return value is returned by the function, and you can store it in a variable just as you can store a literal value, such as a string or number.
If a function should return something, you use the return keyword, usually followed by a value or a reference to what's being returned. However, you can also use return on its own to exit a function.
Here's an example of a return statement that returns a value:
return myVariable;
And here's how you'd use return on its own:
return;
Continuing from our earlier example, you could write a function to create a greeting message and then return the value back to the caller. The return keyword stops the function from running and returns the specified value, if there's one. So you usually want to use return at the end of your function, like this:
function createGreetingMessage(name) {
const message = `Hello, ${name}`;
return message;
}
Note
Variables that you define inside a function can't be accessed from anywhere outside the function. These variables are called local variables. Outside the function, they're considered out of scope.
When you call this function, you store the value in a variable. You store the value in much the same way as you would set a variable to a static value (for example, let name = 'Christopher'), like this:
let greetingMessage = createGreetingMessage('Christopher');
Return values help demonstrate another reason why functions are such an important part of JavaScript. You can reuse the same function with different arguments to produce multiple return values.