Why document.getElementById('catSel') Returns Null in JavaScript

---
Disclaimer/Disclosure: Some of the content was synthetically produced using various Generative AI (artificial intelligence) tools; so, there may be inaccuracies or misleading information present in the video. Please consider this before relying on the content to make any decisions or take any actions etc. If you still have any concerns, please feel free to write them in a comment. Thank you.
---

Element Not Present in DOM

The most straightforward reason is that the element with the ID catSel does not exist in your HTML document. Double-check your HTML to ensure that there is an element with this specific ID.

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

Case Sensitivity Issues

JavaScript is case-sensitive when it comes to IDs. Make sure the ID you are using in your JavaScript exactly matches the ID in your HTML.

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

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

Code Execution Timing

Solution 1: Placing Script at the End of the Body

Place your script tag at the end of the body so that all elements are loaded before the script runs.

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

Solution 2: Using DOMContentLoaded Event

Alternatively, you can wrap your code inside a DOMContentLoaded event listener to make sure it runs only after the DOM is fully loaded.

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

Script Errors

If there are script errors earlier in your code, it might prevent the script from executing subsequent lines correctly. Check for any errors that might be halting your code.

Incorrect HTML Structure

Sometimes, incorrect or malformed HTML can cause elements not to be recognized correctly. Validate your HTML to make sure there are no issues.

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