Interactive Courses
Frontend, AI and engineering concepts, explained step by step. See how each idea works, then put it into practice at your own pace.
Free
JavaScript Memory and Garbage Collection
Find out what keeps an object alive, why apps leak memory, and how the browser cleans up without freezing the page.
Free
JavaScript Fundamentals
Know another language? Learn the core of JavaScript by building a mock interview booking page: variables, types, conditionals, loops, functions, arrays and objects. Predict what each line prints.
Premium
How the Browser Runs and Renders Your Code
The event loop and rendering, one step at a time. Predict any output order, and fix a page that freezes.
Premium · Minimum Yearly plan
Client-Side State and Data Sync
Keep a page fast and correct when its data lives on a server. Query caches, normalized stores, server rendering, optimistic updates, sync and offline, one step at a time.