Get the Preplance app for a seamless learning experience. Practice offline, get daily streaks, and stay ahead with real-time interview updates.
Get it on
Google Play
4.9/5 Rating on Store
Amazon · React
Practice React questions specifically asked in Amazon interviews – ideal for online test preparation, technical rounds and final HR discussions.
Questions
11
Tagged for this company + subject
Company
Amazon
View company-wise questions
Subject
React
Explore topic-wise practice
Go through each question and its explanation. Use this page for targeted revision just before your Amazon React round.
ReactDOM.render() mounts or updates React elements into the DOM. It connects your React app to a real HTML container, typically linking JavaScript logic to browser display.
ReactDOM.render(<App />, document.getElementById('root'));For complete preparation, combine this company + subject page with full company-wise practice and subject-wise practice. You can also explore other companies and topics from the links below.
React is a component-based JavaScript library for building reusable UI elements and handling user interface logic efficiently.
setState() schedules an update to the component’s state and re-renders it. It can also accept a callback that runs after the update is complete.
React is only a library, not a full framework. It requires learning JSX and other tools like routing or state management separately. Beginners might find it complex due to the large ecosystem.
React keeps two versions of the Virtual DOM—previous and current. When a change occurs, React compares them (diffing) and updates only the changed parts in the real DOM, making rendering fast and efficient.
In functional components, props are received as function arguments. In class components, they are accessed via this.props. Props are read-only in both cases.
// Functional
function Hello(props) { return <p>{props.name}</p>; }
// Class
class Hello extends React.Component { render() { return <p>{this.props.name}</p>; } }In React Router v6, you can redirect users using the Navigate component after successful login. Once authentication succeeds, set a state like isLoggedIn to true and conditionally render <Navigate to='/dashboard' /> to send the user to the dashboard automatically.
if (isLoggedIn) return <Navigate to='/dashboard' />; else return <LoginForm />;
Global state can be handled using Redux for predictable centralized state, Context API for lightweight shared state, or Zustand for simpler and faster store-based state management without boilerplate.
The command 'npm install -g create-react-app' globally installs the tool for creating new React projects quickly.
You can build a custom hook that syncs state with localStorage. Whenever state changes, save it to storage and initialize from storage on load.
function useLocal(key,init){
const [val,setVal]=useState(()=>JSON.parse(localStorage.getItem(key))||init);
useEffect(()=>localStorage.setItem(key,JSON.stringify(val)),[val]);
return [val,setVal];
}React is an open-source JavaScript library developed by Facebook (now Meta) for building user interfaces, especially single-page applications. It helps developers create reusable UI components that update efficiently when data changes.