Resolving Global Variable Issues in AWS Lambda Functions Using Node.js

Learn why global variables may not update as expected in AWS Lambda functions and discover effective strategies to manage them properly.
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The Problem: Unupdated Global Variable

Let’s start with an example scenario. You have an AWS Lambda function designed to process a webhook. This function receives a POST request with an ID, processes it, and you expect to update a global variable with this ID.

Here’s a simplified version of the code:

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

Behavior You Might See

Why This Happens

Breakdown:

The entire script is loaded, and it sets newDealId to an empty string.

When the handler is invoked (during a webhook request), it updates newDealId, but the log outside the function does not refer to that execution.

Solution: Structure Your Code for Clarity

To resolve this issue, it is critical to ensure that any references to variable values are made within the context where they are valid or accessible. Here’s an alternative approach to structure your function:

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

What Changed?

Local Variable Declaration: The variable newDealId is declared within the handler, ensuring it starts as an empty string.

Function Invocation: The logic for assigning the ID and returning the response is encapsulated in the doesStuff function. This ensures the correct ID is processed during invocation.

Conclusion

By restructuring how and where you use your variables within AWS Lambda functions, you can avoid the pitfalls of unexpected behavior with global variables. In summary, always remember that:

Global variables set outside of function execution are typically read-only until the corresponding function runs.

Ensure your variable usage is encapsulated in the correct execution context for reliable results.

With these insights, you can confidently handle global variables in your AWS Lambda functions and improve your code's reliability.

If you have experienced similar issues or have any questions, feel free to share your thoughts in the comments!