How to Exit from a Function in JavaScript

When you're coding, you sometimes want to exit from the middle of a function.

This is useful for when you want to stop the further execution of the code, or to return a value you have already generated.

In this post, we'll learn how to exit from a function in JavaScript.

How to Exit from a function

Let's say you have a function that takes in two numbers and adds them.

However, you want to exit from the function if either number is negative.

Here's how that looks like:

	const sum = (num1, num2) => {
    if (num1 < 0 || num2 < 0) {
        return -1;
    }

    return num1 + num2;
}

Notice how we can immediately exit the function by using the return keyword.

This is a great way to validate that the parameters passed in are valid, or simply to return back the user a value once it has been calculated.

Here's an example of a greeting that requires a name to be passed in.

	const greeting = (name) => {
    if (!name) {
        return "Please pass a name!";
    }

    return `Hello, ${name}!`;
}

console.log(greeting("John"));
console.log(greeting());

	Hello, John!
Please pass a name!

Conclusion

In this post, we learned how to immediately exit a function.

Just use the return keyword to exit from a function and the rest of the function will not execute.

Thanks for reading!

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