React
Components, state, effects, and the performance instincts that keep a UI honest. The library most product teams still hire for.
Mastery unlocks after a 90% Quiz score
Real-world analogy
The UI is a function of state. React is the agreement that when state changes, the screen catches up — without you patching the DOM by hand.
◎ Why it matters in production
Unnecessary re-renders, prop-drilling, and fetching in the wrong place are how 'simple' pages jank. Interviewers can feel this in a take-home.
Fundamental concepts you will master
UI = f(state)
Think in snapshots, not sequences of DOM mutations.
Hooks as subscriptions
useState, useEffect, useMemo — and the dependency array that will haunt you.
Lifting state
Who owns the data? The answer is almost never 'every component'.
Concurrent realities
Transitions, suspense, and why loading states are a design problem.
Step-by-step curriculum
JSX & components
Composition, children, and the difference between a component and a template.
State & effects
Local state, derived state, and effects that don't loop forever.
Data fetching
Where it lives, how it caches, what the user sees while it loads.
Routing & forms
URLs as state, controlled inputs, validation you can trust.
Performance
Keys, memo, virtualisation, and measuring before you guess.
Ready to see it in action?
Build your own path, step through operations, and watch mastery unlock after 90%.
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