It is January 2020! As I start the new year, I have committed to upgrade myself and update my coding skills. I have been doing a lot of coding with HTML and CSS to help build up those skills, but have put aside a lot of the object oriented principles I learned as a Flatiron student. Despite having reviewed some JavaScript just a few months ago, and remembering the foundations and sytax of the language, I needed to practice the development of data structures and algorithms. As they say, use it or lose it, and I was determined not to keep losing it.
So, as I made my return to JavaScript, I wanted to break down the actual concept of return. It seems pretty straightforward, but it’s easy to lose sight of how using the return keyword can affect our results.
Where to Use return
The explicit use of return is primarily inside functions where we want a value returned. However, we have to remember that return does not automatically print anything for us. We will only see the returned value in the console when we invoke, or call, the function.
It should not be confused with console.log(), which is a function that logs, or prints, information to the console. That’s a topic for another day, though.
How return Sets Limits
When we use the return keyword inside the function we are effectively telling the computer to stop evaluating the function. Anything within the function that comes after the return statement will not compute. For instance, as in the example below, we set up a calculation to change the value of the sum variable, and then we want to return something else.
However, if we changed the order in which we want the computer to evaluate the function, and place the return before the rest of what we want evaluated, the return ends the function. Anything inside the function that comes after the return is obsolete.
Lack of return
So, what happens when we don’t explicitly use the return keyword?
As you can see from the image above, the lack of an explicit return implicitly returns undefined. The only thing that changes is the value of the sum variable. In this scenario, invoking the function will not return what we expect the function to return for us.
Conclusion
While the return keyword may not be necessary for the function to run and evaluate the way it was intended, not having it could give us some unintended and confusing results. As with everything we do in code, follow best practices and explicitly use the return keyword to ensure you get the correct result you’re looking for. Ultimately, the trick is to understand what return is suppsed to do in the context of the function we are writing or using.