• Learn by practice: unique and fluent tutorials in koan style.
  • No sandboxes: write code in your own IDE, run it on your own machine.
  • No crowd-sourcing: all exercises are created and solved by expert engineers.
  • Exercise variety: quizzes, tasks, refactorings, etc.

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Callbacks | Async Fundamentals

Write a non-blocking async JS code with callbacks. Learn & practise parallel and sequential control flows, scoping, error handling, composition patterns, etc.

78 exercises

Promises | Async Fundamentals

Streamline the control flow of async JS code with promises. Learn & practise composition patterns, scoping, promise-callback interop., error handling, etc.

73 exercises
11 exercises

Datatypes | JS Fundamentals

Learn more about data types, primitives, and objects. Learn to see differences between dicts, structs, tuples, arrays. Master data declarations, destructuring, spreads, etc.

59 exercises

Functions | JS Fundamentals

Learn more about functions, the main building block of a code in high-level languages. Master concepts like arity, purity, side effects, memoization, mutability, scope, etc.

51 exercises

Node Fundamentals

Solve C10k problem and build scalable web servers with Node. Master platform APIs, builtins, module system, networking, and async IO. From the basics to your own realtime server.

55 exercises

FP with Ramda

Use functions as the main unit of composition and code reuse. Master purity, immutability, closures, currying, lenses, recursion patterns, etc. From basics to your own library code.

80 exercises

React Fundamentals

React is the most popular tool to create single page applications (SPA). SPA are actively supplanting "normal sites", since they do not require a page reload for every user action and provide the best UX (user experience).

46 exercises