Beyond the obvious options...
...it's really hard to say if your own code is "readable" or "maintainable".
The more code you expose yourself to, the more you'll be able to look at it from a distance and judge it's competency. You'll notice patterns, or "smells", that make the code less maintainable or readable (like callback hells or poorly formatted ES6).
If you're forced to search for questions that can't be answered by your documentation, you're not there yet.
There are best practices you can adopt to ensure your code is well documented and formatted correctly. From the code base comments, to the commits, to the docs -- it should be easy to pick up any part of your application and know how to use it.