From my experience, most of the big projects in the JavaScript ecosystem are very welcoming to first time contributors. To make your first "valuable" contribution I'd suggest you pick a project that you are using yourself. Read documentation and turn on notifications for issues on GitHub and very quickly you will realize that a lot of people make small yet valuable contributions (documentation, small refactoring etc) without knowing all the details of the source code. At least that has been my experience so far. Last year when my first "feature code" pull request was merged, I wrote a post about the experience: maurobringolf.ch/2017/07/open-source-9-steps-to-m… Although thats more geared towards contributing long-term rather than just one small first contribution, but maybe it helps anyway.