I tried Codementor once many years ago, but didn't continue using it due to having a much more profitable software contractor career in London. Now I'm semi-retired in Spain and can share my experience with you.
15 years of JavaScript professional experience including 10 years of contracting with top digital agencies and finance consultancies in London. Plus full stack(TypeScript/Node/Postgres) expience in a crypto exchange.
Currently devoted to my personal projects(full stack JavaScript/TypeScript/Postgres/TimescaleDB, and Go). My smaller projects are open source, usually as NPM modules and the big ones will become OS when they're mature enough.
My Stack Overflow https://stackoverflow.com/users/696535/pawel
and Github https://github.com/DVLP/
Some of my current projects:
https://font.skin - GPU text effects rendered in real time using bespoke WebGL engine
https://fin3d.com - An overwierview of S&P 500 stocks with daily updates. It used to have real-time updates with price bar animations but Yahoo Finance recently closed their API.
I spent hundreds of hours profiling and optimizing JavaScript code in my game engine. Turns out most programs can easily run 10x faster, and with some more effort and rewriting, 100x faster. NPM packages should not be trusted. It takes 5 minutes to publish your own NPM module so this place is a performance graveyard full of amateur projects giving a false sense of legitimacy because they instal so elegantly through the CLI. Also NPM modules often contain 20 lines of actual code plus 20 files of config and bloat.
Back in the day (2009/10) I also built the first popular web fonts website https://fontsforweb.com which I published before Google Fonts existed. It's still functioning in a low-maintenance mode with just a few hundred visits per day. It's using PHP with Zend Framework so I can help you with that too.