How to Exit a JavaScript Function

There are times when you need to quickly exit a JavaScript function while it’s executing. Fortunately, you can achieve this by using the return keyword.

When JavaScript encounters the return keyword, it immediately exits the function. Any variable or value passed after return will be returned as the result.

This technique is especially useful when you want to check for a certain condition within the function. For example, let’s say you expect a parameter to be present:

function calculateSomething(param) {
    if (!param) {
        return;
    }

    // Continue with the function
}

In this case, if the param value is present, the function will continue executing as expected. However, if the param value is not present, the function will be stopped immediately.

You can also choose to return an object that describes the error, as shown in the following example:

function calculateSomething(param) {
    if (!param) {
        return {
            error: true,
            message: 'Parameter needed'
        };
    }

    // Continue with the function
}

The specific value or object that you return will depend on how the function is expected to work in the code that calls it. For instance, you might return true if everything is in order, and false if there’s a problem. Alternatively, you can use an object with an error boolean flag, allowing you to check for this property to determine success or failure.