react-junior developer interview notes

answers_to_common_questions.md

Here are clean, interview-ready one-liners + quick examples you can say in a rapid-fire round:

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⚡ Prop Drilling

Answer:

“Prop drilling is when data is passed through multiple intermediate components just to reach a deeply nested child.”

When to mention more:

“It becomes hard to maintain, so we usually use Context API or state management instead.”

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⚡ React Fragment

Answer:

“A Fragment lets you group multiple elements without adding an extra DOM node.”

Example:

<>
  <h1>Hello</h1>
  <p>World</p>
</>

One-liner add-on:

“It keeps the DOM clean.”

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⚡ Arrow Functions

Answer:

“Arrow functions are a shorter syntax for functions and they don’t bind their own this.”

Example:

const add = (a, b) => a + b;

Interview add-on (optional):

“They’re commonly used in React to avoid manual binding.”

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🔥 Ultra-Short Versions (If interviewer is rushing)

• Prop drilling:

  “Passing props through multiple layers unnecessarily.”

• Fragment:

  “Group elements without extra DOM nodes.”

• Arrow function:

  “Short function syntax without its own this.”

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If you want, I can give you a full 30-question rapid-fire sheet like what Eclaro interviewers actually do.

gistfile1.markdown

Here’s a focused prep guide for a React Developer interview at Eclaro — based on what they typically look for (strong fundamentals, real-world experience, and clean coding practices).

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🔥 Core React Questions (Very Likely)

1. What are React Hooks? Why use them?

• useState, useEffect, useContext, useMemo, useCallback

• Why:

  • Replace class components
  • Cleaner state management
  • Better code reuse via custom hooks

👉 Follow-up:

• Difference between useEffect vs useLayoutEffect
• Dependency array behavior

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2. Explain Virtual DOM

• React creates a virtual representation of the UI
• Uses diffing algorithm to update only changed parts
• Improves performance vs direct DOM manipulation

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3. What is the difference between state and props?

State	Props
Mutable	Immutable
Managed inside component	Passed from parent
Triggers re-render	Also triggers re-render

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4. What is lifting state up?

• Moving shared state to a common parent component
• Enables data sharing between siblings

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5. Controlled vs uncontrolled components

• Controlled → React manages form state
• Uncontrolled → DOM manages state (via refs)

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⚙️ Practical / Real-World Questions (Eclaro LOVES these)

6. How do you handle API calls in React?

• fetch / axios
• Usually inside useEffect

useEffect(() => {
  fetch('/api/data')
    .then(res => res.json())
    .then(setData);
}, []);

👉 Bonus points:

• Error handling
• Loading states
• AbortController / cleanup

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7. How do you manage global state?

• Context API (basic)
• Redux / Zustand (advanced)

👉 Expect:

• “When would you NOT use Redux?”

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8. How do you optimize performance?

• React.memo
• useMemo, useCallback
• Code splitting (React.lazy)
• Avoid unnecessary re-renders

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9. Explain key prop in lists

• Helps React identify which items changed
• Must be unique and stable

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10. How do you handle forms?

• Controlled inputs

• Libraries:

  • Formik
  • React Hook Form (🔥 modern favorite)

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🧠 Intermediate / Advanced Questions

11. What are custom hooks?

• Functions that reuse logic across components

function useFetch(url) {
  const [data, setData] = useState(null);

  useEffect(() => {
    fetch(url).then(res => res.json()).then(setData);
  }, [url]);

  return data;
}

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12. What is reconciliation?

• Process React uses to update DOM efficiently
• Based on diffing algorithm

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13. What are React lifecycle equivalents in hooks?

Class	Hook
componentDidMount	useEffect (empty deps)
componentDidUpdate	useEffect (with deps)
componentWillUnmount	cleanup function

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14. What is Context API?

• Avoids prop drilling
• Shares global data (theme, auth, etc.)

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15. What is lazy loading?

• Load components only when needed

const Page = React.lazy(() => import('./Page'));

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💻 Coding / Hands-On Tasks (VERY COMMON)

Eclaro often includes practical tests like:

🧪 Build:

• Todo app
• Search/filter list
• Pagination component
• API dashboard

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🧪 Debug:

• Fix re-render issues
• Identify missing dependencies in useEffect

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🧪 Example question:

“Why is this component re-rendering unnecessarily?”

👉 Expected answer:

• Function recreated → use useCallback
• Object reference changes → use useMemo

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🎯 Behavioral + Project Questions

Expect:

• “Explain your recent React project”
• “How did you handle state?”
• “What challenges did you face?”

👉 Tip: Use STAR method (Situation, Task, Action, Result)

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🚀 Bonus: What Eclaro Typically Values

• Clean, readable code

• Good communication (they’re client-facing)

• Real-world problem solving

• Experience with:

  • REST APIs
  • Agile / Scrum
  • Git workflows

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⚡ Quick Rapid-Fire (They LOVE this)

• What is JSX?
• What is prop drilling?
• What is a fragment?
• Difference: == vs ===
• Arrow functions vs normal functions
• What is debounce/throttle?

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🧠 Pro Tip (This will impress them)

Say something like:

“I focus on preventing unnecessary re-renders and keeping components small and reusable.”

That signals mid–senior level thinking immediately.

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If you want, I can: ✅ Simulate a mock Eclaro interview (with answers + feedback) ✅ Give you a 1-day crash prep plan ✅ Or tailor questions based on your experience level (junior/mid/senior)