What is the Context API and what problem does it solve?
Quick answer
Context provides a value to an entire subtree without prop drilling. Components read it with useContext.
In detail
Prop drilling — passing a prop through many components that don't use it — is painful for global data like theme, current user, or locale. You create a context, wrap part of the tree in its Provider, and any descendant reads it via useContext. Every consumer re-renders when the Provider value changes.
const ThemeCtx = createContext('light');
<ThemeCtx.Provider value="dark"><Toolbar /></ThemeCtx.Provider>
// deep inside:
const theme = useContext(ThemeCtx); // 'dark'Why interviewers ask this: Core to any state-sharing discussion.
Common follow-up questions
- →Why can context cause performance problems?
- →Is context a replacement for Redux?
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