Google Lighthouse flags pages with unused Javascript and presents it to you. As follows:
How to pass the audit? – Removing unused Javascript
To do this, you need to detect them first. For this, use Chrome DevTools. Go to Coverage Tab in this tool and perform your transactions line-by-line here. Detecting the unused code process will be automated.
Building a new tool for removing unused Javascript code
You can also use Tooling. Report, which will enable you to remove the javascript code from your website in a healthy way and complete the migration.
When you use this tool, you have the opportunity to check whether the bundler has some additional features that can be used to remove unused code. In this way, you can complete the process much more advantageously. Some of these functions are as follows: