Understanding the Difference Between console.log Inside Functions vs. Return Values in JavaScript

Discover why `console.log` can show different results compared to return values in JavaScript. We'll break down the reasons behind this common confusion and explain the concept clearly.
---
This video is based on the question stackoverflow.com/q/71452840/ asked by the user 'dustin' ( stackoverflow.com/u/9430769/ ) and on the answer stackoverflow.com/a/71452899/ provided by the user 'Christian Fritz' ( stackoverflow.com/u/1087119/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: console log shows different value than returning the value

Also, Content (except music) licensed under CC BY-SA meta.stackexchange.com/help/licensing
The original Question post is licensed under the 'CC BY-SA 4.0' ( creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( creativecommons.org/licenses/by-sa/4.0/ ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding the Difference Between console.log Inside Functions vs. Return Values in JavaScript

When working with JavaScript, developers often encounter confusing situations where they see different outputs depending on how they log values. One common question that arises is: Why does console.log show a different result than returning a value from a function?

Let’s dive deeper into this question and clarify the possible reasons behind these varying outputs.

The Problem Explained

Consider a scenario where you have a JavaScript object (like a map) and you want to find a value based on a key. You might try using the find method to look for a specific key. However, depending on how you log the results, you might notice discrepancies between the value returned by the function and what gets printed in the console.

Sample Code

Here is a sample code snippet illustrating the issue:

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

In this example, we’re attempting to retrieve and log a value from an object using the find method.

Detailed Breakdown of the Solution

Let’s clarify why you're seeing different results when using console.log inside the function versus when you return a value:

1. Understanding the find Method

The find method returns the first element that satisfies the provided testing function.

In this case, the testing function checks if the key equals a specific id.

If the condition is satisfied, collectionMap[key] (the value associated with the key) is returned.

2. First Case: Logging the Key

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

Here, collection holds the key that matches the condition.

Since the find method returns the key (not the value), logging collection outputs the key itself.

3. Second Case: Logging the Value

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

In this situation, instead of using return, we log the value directly inside the function.

This effectively turns the find method into a logging mechanism rather than a value retrieval method.

Since find does not actually return the value being logged, collection2 will hold the key returned but nothing is properly returned for logging.

4. Conclusion

In summary, the key difference lies in how you utilize the find method:

Returning a value gives you the key.

Logging a value inside the function will merely log the value to the console without actually returning it.

Key Takeaway

To properly retrieve values and log them correctly, you should choose whether you want to return a value or log it, as these actions serve different purposes in JavaScript.

By understanding how these functions work, you can avoid confusion and utilize them effectively in your coding practices!