How to Load a New Script Programmatically in Vanilla JS: Fixing the TypeError Issue

Discover the solution to the `TypeError` when implementing Modernizr in JS. Learn how to properly load scripts in various browsers!
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How to Load a New Script Programmatically in Vanilla JS: Fixing the TypeError Issue

When writing JavaScript code, occasionally you may run into issues, especially when trying to load external scripts based on certain conditions. One common scenario is when you're using tools like Modernizr to check for feature support in the browser, such as the IntersectionObserver. Imagine you're working in an environment where a polyfill needs to be loaded if the feature isn’t supported, but you encounter a frustrating error in certain browsers. This guide is here to guide you through resolving this particular issue.

The Problem Statement

You may face an error reminiscent of the following when attempting to load a polyfill:

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

This issue arises while trying to execute code such as the fragment below:

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

The Solution

To address this issue and ensure your polyfill loads effectively across different environments, it's recommended to use the appendChild method instead of append. Below, we've broken down the steps necessary to implement this fix.

Step-by-Step Fix

Check Feature Support: Using Modernizr is a fantastic way to check if the IntersectionObserver is already supported.

Create the Script Element: Create a new script element, setting the necessary attributes like id and src for the polyfill.

Use appendChild: Instead of append(), use appendChild() to add the script to the body of your HTML document.

Updated Code Example

Here’s how the corrected code looks:

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

Additional Notes

Why appendChild Works: The appendChild() method has been around for a long time and is well-supported across all browsers, including those versions that do not support append().

Race Conditions: If you are still concerned about whether your script is executing on a fully loaded DOM, consider wrapping your code inside a DOMContentLoaded event listener. This way, your script only runs once the HTML has been fully parsed:

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

Conclusion

If you have any questions about this solution, feel free to leave a comment below!