Understanding Why console.log() Returns undefined in JavaScript

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The Problem at Hand

Imagine you're working with a piece of code that processes data and you want to log specific outputs to the console. For example, consider the following situation where you have functions intended to filter data. If after running these functions you see an undefined value, it could lead to confusion, especially for those new to JavaScript.

Example Code Snippet

Here's some example code where this issue arises:

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

Why Does This Happen?

1. Function Return Behavior

In JavaScript, every function has a return value. If a function doesn’t explicitly return a value, it defaults to undefined.

2. What Should Be Returned?

Solutions to Fix the Code

Updated Function Code

Here’s how you can modify the functions to ensure they return meaningful values:

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

Additionally, ensure the other functions handle the return type correctly. For example, here’s how you would adjust the xygen_generator_rating function:

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

Final Output

Now, when you call the xygen_generator_rating and co2_scrubber_rating, it will log the actual output and won’t return undefined.

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

By making these changes, you’ll have a function that properly returns values and avoids confusion with undefined.

Conclusion

Feel free to try these changes in your code and observe how the outputs change!