Arun Dubey’s Post

Recently, I interviewed for multiple Senior React.js & Tech Lead roles — and noticed a pattern. Most interviewers asked basic but frequently repeated questions that test your clarity of concepts + coding approach. Here are the Top 10 common questions I was asked 👇 1️⃣ Call, Apply, Bind → Difference + Polyfill implementation 2️⃣ Flatten an Array without Array.flat() 👉 Input: [1,2,3,[4,5,6,[7,8,[10,11]]],9] 👉 Output: [1,2,3,4,5,6,7,8,10,11,9] 3️⃣ Inline 5 divs in a row without flex/margin/padding (Hint: display: inline-block) 4️⃣ Find sum of numbers without a for loop (Hint: reduce() / recursion) 5️⃣ Deep Copy vs Shallow Copy — behavior & how to achieve it 6️⃣ Promise & Async/Await output puzzle 7️⃣ Find first repeating character (e.g., "success" → "c") 8️⃣ Stopwatch Implementation (Start, Stop, Reset + live timer) 9️⃣ Build a To-Do List (Vanilla JS/React) → optimize re-renders 🔟 Currying for Infinite Sum 👉 sum(10)(20)(30)() → 60 👉 sum(10)(20)(30)(40)(50)(60)() → 210 𝐠𝐞𝐭 𝐞𝐛𝐨𝐨𝐤 𝐰𝐢𝐭𝐡 (detailed 232 ques = 90+ frequently asked Javascript interview questions and answers, 70+ Reactjs Frequent Ques & Answers, 50+ Output based ques & ans, 23+ Coding Questions & ans, 2 Machine coding ques & ans) 𝐄𝐛𝐨𝐨𝐤 𝐋𝐢𝐧𝐤: https://lnkd.in/gJMmH-PF Follow on Instagram : https://lnkd.in/gXTrcaKP #javascript #javascriptdeveloper #reactjs #reactnative #vuejsdeveloper #angular #angulardeveloper

Recently, I interviewed for multiple Senior React.js & Tech Lead roles — and noticed a pattern. Most interviewers asked basic but frequently repeated questions that test your clarity of concepts + coding approach. Here are the Top 10 common questions I was asked 👇 1️⃣ Call, Apply, Bind → Difference + Polyfill implementation 2️⃣ Flatten an Array without Array.flat() 👉 Input: [1,2,3,[4,5,6,[7,8,[10,11]]],9] 👉 Output: [1,2,3,4,5,6,7,8,10,11,9] 3️⃣ Inline 5 divs in a row without flex/margin/padding (Hint: display: inline-block) 4️⃣ Find sum of numbers without a for loop (Hint: reduce() / recursion) 5️⃣ Deep Copy vs Shallow Copy — behavior & how to achieve it 6️⃣ Promise & Async/Await output puzzle 7️⃣ Find first repeating character (e.g., "success" → "c") 8️⃣ Stopwatch Implementation (Start, Stop, Reset + live timer) 9️⃣ Build a To-Do List (Vanilla JS/React) → optimize re-renders 🔟 Currying for Infinite Sum 👉 sum(10)(20)(30)() → 60 👉 sum(10)(20)(30)(40)(50)(60)() → 210 𝐠𝐞𝐭 𝐞𝐛𝐨𝐨𝐤 𝐰𝐢𝐭𝐡 (detailed 232 ques = 90+ frequently asked Javascript interview questions and answers, 70+ Reactjs Frequent Ques & Answers, 50+ Output based ques & ans, 23+ Coding Questions & ans, 2 Machine coding ques & ans) 𝐄𝐛𝐨𝐨𝐤 𝐋𝐢𝐧𝐤: https://lnkd.in/gJMmH-PF Follow on Instagram : https://lnkd.in/gXTrcaKP #javascript #javascriptdeveloper #reactjs #reactnative #vuejsdeveloper #angular #angulardeveloper

Recently, I interviewed for multiple Senior React.js & Tech Lead roles — and noticed a pattern. Most interviewers asked basic but frequently repeated questions that test your clarity of concepts + coding approach. Here are the Top 10 common questions I was asked 👇 1️⃣ Call, Apply, Bind → Difference + Polyfill implementation 2️⃣ Flatten an Array without Array.flat() 👉 Input: [1,2,3,[4,5,6,[7,8,[10,11]]],9] 👉 Output: [1,2,3,4,5,6,7,8,10,11,9] 3️⃣ Inline 5 divs in a row without flex/margin/padding (Hint: display: inline-block) 4️⃣ Find sum of numbers without a for loop (Hint: reduce() / recursion) 5️⃣ Deep Copy vs Shallow Copy — behavior & how to achieve it 6️⃣ Promise & Async/Await output puzzle 7️⃣ Find first repeating character (e.g., "success" → "c") 8️⃣ Stopwatch Implementation (Start, Stop, Reset + live timer) 9️⃣ Build a To-Do List (Vanilla JS/React) → optimize re-renders 🔟 Currying for Infinite Sum 👉 sum(10)(20)(30)() → 60 👉 sum(10)(20)(30)(40)(50)(60)() → 210 𝐠𝐞𝐭 𝐞𝐛𝐨𝐨𝐤 𝐰𝐢𝐭𝐡 (detailed 232 ques = 90+ frequently asked Javascript interview questions and answers, 70+ Reactjs Frequent Ques & Answers, 50+ Output based ques & ans, 23+ Coding Questions & ans, 2 Machine coding ques & ans) 𝐄𝐛𝐨𝐨𝐤 𝐋𝐢𝐧𝐤: https://lnkd.in/gJMmH-PF Follow on Instagram : https://lnkd.in/gXTrcaKP #javascript #javascriptdeveloper #reactjs #reactnative #vuejsdeveloper #angular #angulardeveloper

🚀 JavaScript Polyfill: Implementing bind() from Scratch As a Frontend Developer, understanding how JavaScript works internally gives you a serious edge in interviews. One commonly asked question: 👉 “Can you write a polyfill for Function.prototype.bind?” Let’s break it down 👇 🔹 What does bind() do? Returns a new function Permanently binds this to a given object Supports partial application (pre-filling arguments) Works correctly with the new keyword 🔥 Basic Polyfill if (!Function.prototype.myBind) { Function.prototype.myBind = function (context, ...args) { const fn = this; return function (...newArgs) { return fn.apply(context, [...args, ...newArgs]); }; }; } 🚀 Interview-Level Polyfill (Handles new keyword) if (!Function.prototype.myBind) { Function.prototype.myBind = function (context, ...args) { const fn = this; function boundFunction(...newArgs) { // If used with `new` if (this instanceof boundFunction) { return new fn(...args, ...newArgs); } return fn.apply(context, [...args, ...newArgs]); } // Maintain prototype chain boundFunction.prototype = Object.create(fn.prototype); return boundFunction; }; } 🧠 Why This Matters? Most developers know how to use bind() Few understand how to implement it. Interviewers love this question because it tests: ✔️ this behavior ✔️ Prototypes ✔️ Closures ✔️ apply() usage ✔️ Constructor behavior 💡 Pro Tip for Interviews When explaining: “bind returns a new function with permanently bound this. In polyfill, we store original function reference, return a wrapper, control context using apply, and handle constructor case using instanceof.” Clear. Confident. Complete. ✅ If you’re preparing for JavaScript interviews, mastering polyfills like this is a game changer. call() polyfill apply() polyfill debounce() throttle() Which one should I post next? 👇 #JavaScript #Frontend #Angular #WebDevelopment #InterviewPrep #Polyfills #NodeJS #ReactJS

Top 20 Frontend Interview Questions JavaScript (Advanced) ------------------------------------ 1 Pure Function vs Impure Function 2 What is Closure? Real-world use cases 3 Explain JavaScript Event Loop (Microtask vs Macrotask) 4 Hoisting – var vs let vs const 5 Shallow Copy vs Deep Copy 6 call(), apply(), bind() – differences & usage 7 Debounce vs Throttle (practical scenarios) 8 Currying vs Partial Application 9 Promise lifecycle & states 10 Promise.all vs Promise.race vs Promise.allSettled React --------- 1 How React works internally (Virtual DOM & Reconciliation) 2 useMemo vs useCallback – when to use which 3 React.memo – how it prevents re-renders 4 Controlled vs Uncontrolled Components 5 useEffect dependency array – common mistakes 6 Context API vs Redux – architecture decision 7 Redux workflow (action → reducer → store) 8 Lazy loading in React (React.lazy & Suspense) 9 How to optimize React performance 10 React 18 features (automatic batching, concurrent rendering) ⭐ Frequently Asked Scenario Questions * How do you reduce unnecessary re-renders? * How do you optimize a slow React page? * How do you handle multiple API calls efficiently? * How do you improve Web Vitals? * How do you manage state in a large application #ReactJS #FrontendDeveloper #ReactInterview #JavaScript #WebDevelopment #TechCareers #FrontendEngineer #ReactHooks #InterviewPreparation #CodingCommunity

🚀 JavaScript Interview Question That Confuses 80% Developers Think you truly understand JavaScript’s async behavior? Let’s test it 👇 console.log("Start"); setTimeout(() => console.log("Timeout"), 0); Promise.resolve().then(() => console.log("Promise")); console.log("End"); 👉 What will be the output? Most developers answer: Start Timeout Promise End ❌ That’s WRONG. ✅ Correct Output: Start End Promise Timeout 💡 Why Does This Happen? This happens because of how the Event Loop works in JavaScript. Promise.then() → goes to the Microtask Queue setTimeout() → goes to the Macrotask Queue After the Call Stack is empty → Microtasks run first Then Macrotasks execute Understanding this difference is crucial for writing predictable asynchronous code. 📌 If You’re Preparing for Frontend Interviews, Master These: ✔ Event Loop & Execution Context ✔ Closures ✔ Hoisting ✔ Debouncing vs Throttling ✔ Shallow Copy vs Deep Copy ✔ Async/Await vs Promises ✔ Call, Apply, Bind ✔ This keyword behavior These are frequently asked in React, Next.js and modern JavaScript interviews. Drop your answer in the comments before checking the solution 👇 And share one tricky JS question you’ve faced recently! #JavaScript #FrontendDeveloper #WebDevelopment #ReactJS #NextJS #InterviewPreparation #CodingInterview #SoftwareDeveloper #TechCareers #Programming #100DaysOfCode

𝐅𝐫𝐨𝐧𝐭𝐞𝐧𝐝 𝐃𝐞𝐯𝐞𝐥𝐨𝐩𝐞𝐫𝐬: 𝐒𝐭𝐨𝐩 𝐋𝐞𝐚𝐫𝐧𝐢𝐧𝐠 𝐑𝐚𝐧𝐝𝐨𝐦𝐥𝐲. 𝐒𝐭𝐚𝐫𝐭 𝐋𝐞𝐚𝐫𝐧𝐢𝐧𝐠 𝐒𝐭𝐫𝐚𝐭𝐞𝐠𝐢𝐜𝐚𝐥𝐥𝐲. I’ve created a complete Frontend Development Roadmap + Interview Checklist to help you: ✅ Master core fundamentals (HTML, CSS, JavaScript) ✅ Understand modern frameworks (React, Angular, Vue) ✅ Strengthen problem-solving & debugging skills ✅ Prepare confidently for frontend interviews ✅ Avoid tutorial-hopping & confusion This isn’t just a roadmap. It’s a structured action plan designed to take you from beginner → job-ready. If you're: Starting your frontend journey Switching to frontend Preparing for interviews Feeling stuck despite learning This guide will bring clarity and direction. 📄 Download the PDF. 📌 Follow Esha Tariq for practical tech insights. 🔁 Repost to help another developer grow. Let’s build scalable, beautiful, and performant web experiences together. #frontend #webdevelopment #javascript #react #angular #vuejs #frontenddeveloper #interviewprep #coding #techcareers #roadmap #career

⚛️ Top 150 React Interview Questions – 98/150 📌 Topic: Why Babel? ━━━━━━━━━━━━━━━━━━━━━━ 🔹 WHAT is it? Babel is a JavaScript compiler. It transforms modern ES6+ code and JSX into backward-compatible JavaScript that older browsers can understand. ━━━━━━━━━━━━━━━━━━━━━━ 🔹 WHY do we use Babel? 🔄 JSX Transformation Browsers cannot read JSX. Babel converts it into React.createElement() calls. 🌍 Backward Compatibility Lets you use modern features (Arrow Functions, Classes, Optional Chaining) without worrying about old browsers. 🧩 Polyfilling Support Can inject missing features like Promise, Array.from, etc., so code runs everywhere. ━━━━━━━━━━━━━━━━━━━━━━ 🔹 HOW does Babel work? 1️⃣ What You Write (Modern Code) const Greet = () => { return <h1 className="title">Hello World</h1>; }; 2️⃣ What Babel Generates (Browser-Friendly) var Greet = function Greet() { return React.createElement( "h1", { className: "title" }, "Hello World" ); }; 👉 JSX disappears. 👉 Modern syntax becomes standard JavaScript. ━━━━━━━━━━━━━━━━━━━━━━ 🔹 WHERE / Best Practices ✔ Use Presets Use @babel/preset-env to automatically target specific browser versions. ⚡ Modern Alternatives For new projects, tools like Vite (esbuild/SWC) are faster alternatives to Babel. 🧱 Keep Plugins Minimal Only install required plugins to keep builds fast and lightweight. ━━━━━━━━━━━━━━━━━━━━━━ 📝 SUMMARY (Easy to Remember) Babel is like a language translator 🗣️ You speak modern JavaScript (ES6/JSX), and Babel translates it into an older version (ES5) so every browser understands you. ━━━━━━━━━━━━━━━━━━━━━━ 👇 Comment “React” if this handbook is helping you 🔁 Share with someone preparing for React interviews #ReactJS #ReactInterview #Babel #JavaScript #FrontendDevelopment #Top150ReactQuestions #LearningInPublic #Developers ━━━━━━━━━━━━━━━━━━━━━━

🚀 Day 11/100 – Understanding Prototypes in JavaScript Today I deep dived into one of the most fundamental concepts in JavaScript: Prototypes. 🧠 Problem: How does JavaScript enable inheritance between objects? ✅ Example: function Person(name) { this.name = name; } Person.prototype.greet = function () { console.log(`Hello, my name is ${this.name}`); }; const user1 = new Person("Bunty"); user1.greet(); // Output: Hello, my name is Bunty 💡 What’s Happening Here? Every JavaScript function has a prototype property. Objects created using new inherit from that prototype. Methods defined on the prototype are shared across all instances. This improves memory efficiency. 📌 Why Not Define Method Inside Constructor? If we write: function Person(name) { this.name = name; this.greet = function () { console.log(`Hello, my name is ${this.name}`); }; } Now every instance gets its own copy of greet() ❌ Which increases memory usage. Prototype keeps it optimized ✅ 🧠 Key Learnings: JavaScript uses prototypal inheritance (not classical inheritance). The __proto__ links objects to their prototype. Method lookup happens through the prototype chain. Core JS concepts like Array, Object, Function are built using prototypes. Understanding prototypes makes closures, inheritance, and even React internals easier to grasp. I’m currently open to Frontend Developer opportunities (React / Next.js) and available for immediate joining. 📩 Email: bantykumar13365@gmail.com 📱 Mobile: 7417401815 If you're hiring or know someone who is, feel free to connect. #OpenToWork #FrontendDeveloper #JavaScript #Prototypes #ReactJS #ImmediateJoiner #100DaysOfCode