Comments are lines of code that JavaScript will intentionally ignore. Comments are a great way to leave notes to yourself and to other people who will later need to figure out what that code does.

Unfortunately JavaScript doesn't yet support comments in regular expressions, so this library rewrites your RegExp strings to remove them before they're handed to the parser ...

This gives Google’s spider, GoogleBot, the ability to read comments in AJAX or JavaScript, such as Facebook comments or Disqus comments and others that are dynamically loaded via AJAX or JavaScript.

Google has started indexing AJAX and JavaScript content. This includes, for example, the Facebook Comments Box many sites use to power their commenting system.