Fixing JavaScript Code: How To Ensure Your Function Returns Values Instead of undefined

Learn how to debug your JavaScript function to return appropriate values for patient heart rates instead of undefined.
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This video is based on the question stackoverflow.com/q/66557671/ asked by the user 'Ron Jeremy' ( stackoverflow.com/u/15358094/ ) and on the answer stackoverflow.com/a/66557851/ provided by the user 'Dhara' ( stackoverflow.com/u/4923027/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Debugging Your JavaScript Code for Accurate Heart Rate Diagnosis

Debugging JavaScript can be quite a challenge, especially when functions return unexpected values like undefined. This post will explore a common problem faced during the implementation of a diagnostic function for categorizing heart rates and provide a detailed solution to fix it.

The Problem: Function Returning undefined

When trying to diagnose patients based on their heart rates, you've written the following function:

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

The function aims to categorize heart rates but only gives undefined. The problem lies in the placement of the variable currentPatient and other minor issues in your code. We’ll explore the solution step by step below.

Steps to Fix the Issue

1. Move currentPatient Inside the Loop

Currently, the line var currentPatient = data[i]; is executed outside the loop, and it won’t get the updated heart rate for each iteration. Instead, the variable should be defined within the loop, capturing the current patient’s heart rate on each iteration.

2. Remove Unnecessary toString Calls

When you're pushing strings into the patients' array, using toString() is redundant because JavaScript automatically converts numbers to strings when you concatenate them with another string.

3. Decide on Output Format

Lastly, you have a choice regarding how you want the output formatted—either as an array or as a string. This guide will show both methods for your convenience.

4. The Correct Code

Here's the revised version of your function, making the necessary adjustments:

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

Example Data Input

To test your function, you can use the following sample array of heart rates:

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

Conclusion

With these adjustments, your function should return the correct values for each heart rate, presenting them in a clear and organized manner. Whether you choose an array or a string output, your diagnostics should now function as intended, categorizing heart rates into "Normal," "Bradycardia," or "Tachycardia." Don’t hesitate to reach out with any further questions about debugging in JavaScript!