I find javascript files difficult to read and follow especially when they were written by someone else and your job is to modify or fix what isn’t working. Often the script contains thousands of lines and it’s unclear which objects the javascript actions are applied to.
There are some good comments in the scripts but not in a consistent format recommended by standards. In this situation, I find it easy to first generate web-based documents using JSDoc and start from there.
Since I don’t the admin access, I downloaded and installed locally
npm install jsdoc
jsdocs myjavascript.jsThis created a webpage reference to all functions with any comments or annotations.