cognate.dev
interactive tutorials, anchored on JavaScript

Same brain, new syntax.

You already know how to program. Each tutorial here starts from JavaScript and maps a new language onto what you already know — side-by-side code, live in-browser playgrounds, and the handful of ideas that genuinely have no JS equivalent.

Compare, don't re-learnEvery concept is shown next to its JS counterpart, so you're translating, not starting from zero.
Run it, don't just read itPlaygrounds run real code in your browser wherever an in-browser runtime exists for the language.
The gaps get flaggedIdeas with no JS analog — Python's GIL, Rust's borrow checker, Go's goroutines — are called out directly, not glossed over.
Nothing to installEvery tutorial is a static page. Open it and start; no accounts, no setup.

Tracks

Pick the language you're learning next.

Python
python-from-js/
Live

Syntax, comprehensions, decorators, the async model, and where Pydantic fits in.
Rust
rust-from-js/
Planned

Ownership and borrowing, the type system, and life without a garbage collector.

Go
go-from-js/
Planned

Goroutines and channels vs. Promises, structs vs. objects, and explicit error returns.

Java
java-from-js/
Idea

Static typing, interfaces, and the JVM's take on concurrency.