Return Early Pattern

The Return Early Pattern

This:

function getErrorMessage(someObject) {
    let errorMessage;
    if (someObject && someOtherObject) {
        errorMessage = "This isn't working because of a tornado.";
    } else if (someObject || someOtherOtherObject) {
        errorMessage = "You're not allowed to visit";
    } else {
        errorMessage = "I don't know what happened."
    }
    return errorMessage;
}

is not as readable as this:

function getErrorMessage(someObject) {
    if (someObject && someOtherObject) {
        return "This isn't working because of a tornado.";
    }
    if (someObject || someOtherOtherObject) {
        return "You're not allowed to visit.";
    }
    return "I don't know what happened.";
}

• Performance is better (not that significant)
• Pattern only makes sense if return statements aren't scattered all over the place

Source: I learned this during code review at work.