How to Fix the Undefined Output in Your FizzBuzz JavaScript Function

Learn why you’re getting `undefined` when calling your FizzBuzz function in JavaScript and how to fix it easily!
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Troubleshooting the FizzBuzz JavaScript Function: Avoiding Undefined Outputs

Have you ever encountered a situation where your JavaScript function, particularly one for FizzBuzz, displays undefined instead of the expected results? If you're seeing this message while using a console in Chrome, you're not alone! Many developers face this issue, but don't worry—I’m here to help clarify the problem and walk you through an effective solution.

Understanding the FizzBuzz Challenge

To begin, let's revisit the expectations of a typical FizzBuzz implementation:

Count from 1 to 100.

For numbers divisible by 3, output "Fizz."

For numbers divisible by 5, output "Buzz."

For numbers divisible by both 3 and 5, output "FizzBuzz."

Output the number itself when it doesn’t meet any of these conditions.

Here is the initial JavaScript function you might be starting with:

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Why the Output is Undefined

When you run the fizzBuzz function in the console, it does not return anything explicitly, leading JavaScript to default to returning undefined. In your provided code, the output variable accumulates the results correctly, but unless you explicitly return this variable or log it to the console, nothing will be displayed.

How to Resolve the Undefined Output Issue

The solution to getting your expected output instead of undefined involves two primary steps: fixing variable scopes and ensuring you log or return results from your function.

Step 1: Use var Instead of let

JavaScript uses different scopes for let and var. While let creates block-level scope, var promotes variables to function scope. This aspect can cause issues with the value of count you are using, leading to potential undefined results. To resolve this, you can simply replace let with var as follows:

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Step 2: Return the Output Array

To display the results of your FizzBuzz function, you can either return the output array or log it directly on the console. Here’s how to adjust your function:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Calling the Function

Finally, to see the result in the console, make sure you call the function and log it appropriately:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following through with these two simple steps—using var instead of let and ensuring that you return your output—you can resolve the undefined output issue you're facing. Now your FizzBuzz function should work as intended, displaying an array filled with numbers, Fizz, Buzz, and FizzBuzz. Happy coding!