react interview questions hindi
React Interview Questions Hinglish Me — Fresher Ka 7 Din Ka Plan
React Interview Questions Hindi/Hinglish Me — Pehle Yeh Padh Le
Bhai scene yeh hai — MERN stack seekh liya, do-teen tutorials follow kar liye, resume pe "React.js" likh diya. Phir interview call aata hai aur pehla sawaal aata hai "React kyun use karte ho, plain JavaScript se kya problem thi?" — aur dimaag blank. Concept aata hai, par bolne ki practice nahi thi.
Yeh blog exactly wahi gap bharne ke liye hai. Neeche 7 din ka plan hai, har din ek topic cluster, aur har cluster ke woh React interview questions jo Indian freshers ko sach me pooche jaate hain — TCS, Infosys, Wipro jaise service-based me bhi aur chhote product startups me bhi. Har question ka chhota model answer diya hai (2-3 line, jitna interview me bolna hota hai), aur depth ke liye tumhe React chapter pe bhej diya jayega — wahan poora question bank, notes aur practice hai.
Rule ek hi hai: har answer bol ke practice karna hai. Mann me padhna interview me kaam nahi aata.
Din 1 — React Kya Hai + JSX
Yeh warm-up day hai. Interview ka pehla sawaal aksar yahin se aata hai, aur pehla impression yahi banta hai.
Q. React kya hai? React ek open-source JavaScript library hai, Meta ne banayi, user interfaces banane ke liye. Ismein UI ko chhote reusable components me todte hain, aur ek virtual DOM ki wajah se sirf jo hissa badla hai wahi dobara draw hota hai.
Q. React library hai ya framework? Library. Woh sirf UI layer handle karta hai — routing, data fetching, state management ke liye alag tools (React Router, Redux) lagte hain. Angular framework hai kyunki woh sab kuch khud deta hai.
Q. Virtual DOM kya hai aur kyun faayda hai? Virtual DOM real DOM ka ek halka JS copy hai. Jab state badalti hai, React naye aur purane copy ko compare karta hai (reconciliation) aur sirf badle hue nodes real DOM me update karta hai — poora page dobara nahi banta.
Q. JSX kya hai? JSX JavaScript ka syntax extension hai jisse JS ke andar HTML-jaisa markup likh paate ho. Browser JSX nahi samajhta — compiler ise plain JS function calls me badal deta hai jo React elements return karte hain.
Q. JSX me class kyun nahi likhte?
Kyunki class JavaScript ka reserved keyword hai, isliye className use hota hai. Isi tarah for ki jagah htmlFor, aur attributes camelCase me — onClick, tabIndex.
Din 2 — Components, Props Aur Conditional Rendering
Q. Component kya hai? Component UI ka ek independent, reusable tukda hai — ek JavaScript function jo JSX return karta hai. Navbar, Button, Card — sab alag components, ek jagah banao, kai jagah use karo.
Q. Props kya hain? State se kya farq hai? Props parent se child ko diye gaye read-only inputs hain, data flow ek-taraf (top-down) hota hai. State component ke apne paas hoti hai aur woh khud usko badal sakta hai. Ek line me: props tumhe diye jaate hain, state tumhari apni hai.
Q. Props drilling kya hai? Jab ek value 3-4 level neeche ke component ko chahiye aur tum use har beech wale component se manually pass karte ho — woh props drilling hai. Iska solution Context API hai (Din 6 me).
Q. Conditional rendering kaise karte ho?
Condition ke hisaab se alag JSX return karte hain — ternary (isLoggedIn ? <Dashboard /> : <Login />), logical && (jab sirf dikhana/chhupana ho), ya component ke start me early return.
Detail me example aur code line-by-line breakdown React chapter me hai — yahan sirf bolne wala version rakha hai.
Din 3 — State Aur useState (Sabse Important Din)
Agar time kam hai to yeh din mat chhodna. Fresher React interview ka centre yahi hai.
Q. useState kya karta hai?
useState ek hook hai jo function component ko apni local memory deta hai. Woh ek jodi return karta hai — current value aur ek setter function: const [count, setCount] = useState(0).
Q. Setter call karne se kya hota hai?
Value update hoti hai aur ek re-render schedule hota hai, taaki screen pe nayi value dikhe. Seedha count = 5 likhne se kuch nahi hoga — React ko pata hi nahi chalega.
Q. setCount(count + 1) aur setCount(c => c + 1) me kya farq hai?
Functional wala form hamesha latest state pe kaam karta hai. Jab nayi value purani value pe depend karti hai — jaise ek hi event me do baar increment — tab functional update stale value ka bug bacha leta hai.
Q. Hooks ke rules kya hain?
Hooks hamesha component ke top level pe call karo — kisi if, loop ya nested function ke andar nahi. Aur sirf React function components ya custom hooks ke andar. Wajah: React hooks ko call ke order se track karta hai.
Aaj hi ek chhota counter bana lo. Chapter me counter project step-by-step hai, aur interview me "kya banaya hai" ka ek asli jawab ho jayega.
Din 4 — Lists, Keys Aur Forms
Q. List kaise render karte ho?
Array pe .map() chala ke elements banate hain, aur har element ko ek unique key prop dete hain.
Q. key kyun chahiye?
Key se React do renders ke beech items ko match kar paata hai — kaun sa item wahi hai, kaun naya, kaun hata. Bina key ke React ko guess karna padta hai aur wrong DOM reuse ho sakta hai.
Q. Index ko key banana galat kyun hai?
Jab items add, remove ya reorder ho sakte hain, tab index shift ho jaata hai — React galat item ko purana samajh leta hai, jisse input ki value ya UI state ulti-seedhi ho jaati hai. Stable unique id use karo (jaise DB ka id).
Q. Controlled aur uncontrolled component me farq?
Controlled input ki value React state se chalti hai (value + onChange) — state hi single source of truth hai. Uncontrolled input apni value DOM me rakhta hai aur ref se padha jaata hai. Interviews me controlled hi default expected hai.
Q. Form submit pe e.preventDefault() kyun?
Warna browser ka default behaviour chalega aur page reload ho jayega — React app ki saari state udd jayegi.
Aaj form + todo wale do chhote projects karo. Yeh do cheezein state, events, lists aur keys — sab ek saath cover kar deti hain.
Din 5 — useEffect Aur Custom Hooks
Q. useEffect kya hai? Ek hook jo render ke baad side effects chalata hai — API call, subscription, timer, document title set karna. Matlab woh kaam jo rendering ka hissa nahi hain.
Q. Dependency array ka kya role hai?
Woh decide karta hai effect kab dobara chale. [] = sirf ek baar (mount pe), [value] = jab value badle, aur array na do to har render pe chalega.
Q. Cleanup function kya hai?
useEffect se jo function return karte ho woh cleanup hai. Woh agle effect se pehle aur component unmount hone pe chalta hai — timer clear karne, event listener hatane ya socket band karne ke liye.
Q. useEffect ke andar API call kaise?
Ek async function andar define karke call karo (effect callback khud async nahi hona chahiye), response ko state me set karo, aur loading/error state bhi rakho. Component unmount ho jaye to stale update se bachne ka intezaam bhi mention kar dena — yeh senior touch hai.
Q. Custom hook kya hai?
Ek normal JavaScript function jiska naam use se shuru hota hai aur jo andar doosre hooks call karta hai. Isse repeat hone wali stateful logic (jaise useFetch, useLocalStorage) alag nikaal ke reuse kar sakte ho, bina component hierarchy badle.
Din 6 — Context API, Redux Basics Aur Routing
Q. Context API kya hai?
React ka built-in tareeka hai value ko poore component tree me share karne ka, bina har level pe props pass kiye. createContext se context banao, Provider se value do, aur kisi bhi descendant me useContext se padho.
Q. Context aur Redux me kab kya use karoge? Context chhoti, kam badalne wali global values ke liye theek hai — theme, logged-in user, language. Redux tab jab state badi ho, kai jagah se update ho, aur tumhe predictable flow + debugging chahiye.
Q. Redux ka basic flow kya hai? Poori app state ek single store me rehti hai. State read-only hai — badalne ke liye ek action dispatch karte ho, aur pure reducer function purani state + action lekar nayi state return karta hai. Aaj ka standard tareeka Redux Toolkit hai.
Q. React Router kya karta hai? Yeh client-side routing library hai jo URL paths ko components se map karti hai aur view badalti hai bina full page reload ke, browser ke History API se URL sync rakhte hue.
Din 7 — Performance + Full Mock
Q. React.memo, useMemo, useCallback — teeno ka farq?
React.memo ek component ka rendered output cache karta hai, useMemo ek computed value cache karta hai, aur useCallback ek function reference cache karta hai. Teeno tab skip karte hain jab dependencies nahi badli — unnecessary re-renders rokne ke liye.
Q. Har jagah useMemo laga dena chahiye? Nahi. Memoization ka apna cost hai (comparison + memory). Pehle measure karo, jahan sach me heavy computation ya bada list re-render ho wahin lagao. Yeh answer interviewer ko sabse zyada pasand aata hai kyunki maturity dikhati hai.
Q. Ek slow React page ko kaise debug karoge? React DevTools Profiler se dekhoge kaunsa component baar-baar render ho raha hai, phir wajah pakdoge — galat key, har render pe naya object/function prop, ya state upar rakhi hui jahan zarurat nahi thi.
Aaj ke baad sirf padhna band. Bol ke poora set practice karo — AI mock interview pe TCS/Infosys style round chala lo, awaaz record hoti hai aur feedback turant milta hai. Ghar pe akela bolne me jo jhijhak hai, wahi interview me nuksan karti hai.
Service-based Vs Product-based — Sawaal Kaise Badalte Hain
- Service-based (TCS, Infosys, Wipro, Cognizant): definitions aur clarity zyada matter karti hai. "React kya hai", "state vs props", "useEffect kya karta hai" — clean, textbook-jaise answers chahiye. Ek chhota project + HR round pe bhi utna hi weight hota hai.
- Product-based / startups: "kyun" zyada aata hai. Yeh component kyun re-render ho raha hai, state kahan rakhoge, Context lete ya Redux — aur live coding round ki sambhavna zyada.
Dono ke liye base wahi 7 din hai, bas Din 7 wale "kyun" wale answers product interviews me zyada dohrao. Company-wise pattern samajhna ho to TCS aur Infosys interview questions wala blog padh lo.
Resume Ka Angle — Yeh Mat Bhoolna
Ek baat jo log miss karte hain: React kitna bhi aata ho, interview call tabhi aayega jab resume shortlist hoga. Zyaadatar fresher resumes ATS me hi atak jaate hain — skills section me "React" likha hai par JD ke keywords (React.js, Hooks, Redux, REST API) match hi nahi karte.
Interview prep ke beech 20 minute nikaal ke apna resume free ATS checker pe daal do aur score dekh lo. Aur haan — resume me sirf wahi likhna jo tum defend kar sako. "Redux" likha hai to Din 6 wale saare answers ready hone chahiye.
Aage Kya
Yeh 7 din ka plan structure deta hai, depth nahi — depth chapter me hai. Har topic ke poore notes, code walkthrough, practice questions aur flashcards yahan hain: React interview prep chapter.
Plan simple rakho — roz ek cluster padho, us cluster ke questions bol ke answer do, weekend pe ek full mock. Sat din baad tumhare paas ratta nahi, bolne layak React hoga. Aur interview me farq wahi banata hai.
FAQ
React interview ki taiyari kitne din me ho jaati hai?
Agar tumne pehle se React me 1-2 chhote projects banaye hain, to 7 din ka focused revision kaafi hai — roz 2 se 3 ghante. Bilkul zero se shuru kar rahe ho to 7 din me sirf basics aur ek project ho payega, aur usi ke around interview handle karna padega. Plan yeh hai ki har din ek cluster (state, effects, lists) pakdo aur usko bol ke revise karo.
Fresher React interview me sabse zyada kya pucha jaata hai?
Sabse common cluster hai — React kya hai aur virtual DOM kaise kaam karta hai, state vs props ka farq, useState aur useEffect, lists me key kyun chahiye, aur controlled form kya hota hai. Iske baad interviewer aksar tumhare apne project pe ghuma deta hai, isliye project ka har decision explain karne layak hona chahiye.
Kya React interview me Redux aana zaroori hai?
Fresher role ke liye Redux ka deep knowledge zaroori nahi, par basic samajh honi chahiye — store, action, reducer, aur yeh ki Redux Toolkit modern standard tareeka hai. Agar tumne resume me Redux likha hai to phir detail me poocha jayega, isliye jo likha hai wahi bolne layak rakho.
React interview me answer English me dena zaroori hai?
Explanation Hinglish ya Hindi me de sakte ho, aur zyaadatar Indian interviewers ko iss se koi problem nahi hoti. Par technical terms — state, props, re-render, dependency array — English me hi bolo, kyunki wahi standard vocabulary hai. Best formula: definition ek line English me, samjhaana apni bhasha me.
Bina experience ke React project me kya banaun?
Counter, ek form with validation, aur ek todo app — yeh teen cheezein milke React ke saare core concepts cover kar deti hain: state, events, controlled inputs, lists aur keys. Inhe deploy karke live link resume me daalo. Ek acha samjha hua chhota project, das adhoore cloned projects se zyada kaam aata hai.
Coding round me React ka kya poocha jaata hai?
Aksar chhota UI task milta hai — ek counter, ek search filter jo list ko filter kare, ya ek form jo submit pe data dikhaye. Yeh dekha jaata hai ki tum state kahan rakhte ho, event handle kaise karte ho, aur map/key sahi use karte ho ya nahi. Speed se zyada soch samajh ke likhna important hai.