How to Fix document.querySelector(...) is null Error in JavaScript Point Calculation

Learn how to troubleshoot and fix the common JavaScript error that prevents point calculations in your survey application, ensuring smooth operation and accurate scoring.
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Troubleshooting JavaScript Point Calculation Issues in Your Survey App

Understanding the Issue

When using JavaScript to calculate points based on user selections, you may be running into an issue where the selected answer for a question is not found. This could be due to multiple reasons:

Incorrect logic: The loop might be attempting to access answers even when they are not selected, causing your script to fail.

The Solution

Step 1: Update the Calculation Function

We need to ensure that the point calculation only occurs if there is a selected answer for the question. Let's revise the JavaScript code:

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

Key Changes:

Conditional Check: We added a check with if (selectedAnswer). This ensures that we only proceed to add points when a selection has been made.

Loop Update: The loop will work for each question; you can adjust the number of iterations (i <= 2) according to the total number of questions in your survey.

Step 2: Update HTML Structure

Here’s an example of how the HTML should look:

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

Summary of Steps

Check for User Selection: Before accessing the .id of the selected radio input, ensure the input exists.

Update Your Code: Make the required modifications in your JavaScript function to incorporate condition checking.

Test Your Survey: Run your survey application and check if the points accumulate correctly based on user selections.

Final Thoughts

By implementing the checks proposed in this guide, your survey application should handle point calculations gracefully, even when some questions have not been answered. Always ensure to handle possible null values when working with the Document Object Model (DOM) in JavaScript, as this practice will help avoid common errors and provide a smoother user experience. Happy coding!