What Triggers This Issue?
Heavy and unnecessary JS files are usually caused by third-party codes (social sharing buttons, for example), plugins, or page builders your website uses. Besides, it can happen if you forget to delete some lines of code used for testing or other temporary purposes.
How To Check the Issue
Make a full audit to find out and fix your technical SEO in order to improve your SERP results.
Why Is This Important?
Unused functions will slow down your website’s loading speed because the browser has more work to do, including downloading, parsing, compiling, and evaluating the useless script. It delays the rendering parameter and consumes more cellular data. This affects the website’s performance and will eventually cause a poor user experience.
How To Fix the Issue
Here are several hints on how to fix the problem and improve your website performance:
- You may use some web developer tools such as Lighthouse. Although, this one will report the unused code on a particular page. You should be careful before removing it, as the code might still be used on another page.
- Try minifying JS to get rid of unnecessary characters from the code. The closure compiler will help you with that.
- Delaying non-critical JS of the page will also help reduce the browser execution time. Another way is to defer non-essential scripts using a cache plugin.