Build to understand

ABC of Programming is a set of hands-on modules built around solving problems and discovering the concepts along the way. No videos to watch, no badges to earn.

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eval.js

function evaluate(expr) {
  return match(expr, {
    "n": (n) => n,
    "read": (name) => get(name),
    "if": (cond, then, alt) =>
      evaluate(cond) ?
        evaluate(then) : evaluate(alt),
    // ...
  });
}

Build it yourself

Each problem extends what you've already built. By the end of a module, you've made something complete that you understand from the inside out.

No hidden magic

A closure isn't magic that 'remembers' variables. It's a function bundled with its environment, and you build exactly that.

Nothing to memorize

No sign-up, no video lectures, no gamification. You work through problems and build understanding by doing, not by being told.

Featured Module

Build an Interpreter

End up with a working language

Build a small language you can actually run, one that handles variables, functions, and data structures. You grow it from scratch, one capability at a time, starting with evaluating a single number.

JavaScript Environments Closures Recursion

Start this module

Work through problems in your browser with instant feedback.

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Who this is for

If you'd rather build something than watch a video explaining it, this is for you. Maybe you want to understand a subject deeply instead of just getting through it, or maybe you just enjoy taking things apart to see how they work. Both belong here.

How it works

1

Open a module

Each module builds one complete system from scratch.
2

Solve problems in order

Every problem extends your previous code, guided by tests.
3

Understand from the inside

No black boxes. You wrote every line, so you know how it works.

No sign-up. Open the module and start building.

More modules in development.