JavaScript Event Loop Explained

🚀 **JavaScript Interview Question** What will be the output of this code? ```js const obj = { a: { b: 0 } }; const v1 = obj?.a?.b || 42; const v2 = obj?.a?.b ?? 42; console.log(v1, v2); ``` 🤔 **Think before you scroll...** --- #JavaScript #Frontend #WebDevelopment #CodingInterview #ReactJS

🚨JavaScript Interview Question What will be the output? function greet(name) { if (name === undefined) { console.log("Hello, guest!"); } else { console.log("Hello, "+ name); } greet(); greet("Anas"); greet("Anas", "How are you?"); Looks simple... but there's a twist What will be the output? Why does the last call behave differently? Bonus: How does JavaScript handle extra arguments? #JavaScript #FrontendInterview #WebDevelopment #CodingInterview #ProductBasedCompany

💡 **Daily React/JavaScript Interview Tip** The event loop isn’t just theory—it explains **why your code runs in a certain order**. 👉 Weak answer: “The event loop handles async operations.” ✅ Stronger answer: “JavaScript is single-threaded, so it uses the event loop to manage async tasks. Synchronous code runs first, then callbacks from the task queue (like `setTimeout`) and microtask queue (like Promises) are processed. Microtasks always run before the next task, which is why Promise callbacks execute before `setTimeout`.” 🧠 Example: ```js console.log('A'); setTimeout(() => console.log('B'), 0); Promise.resolve().then(() => console.log('C')); console.log('D'); ``` 👉 Output: A D C B 📌 Tip: If you can clearly explain **call stack, task queue, and microtask queue with an example**, you’ll stand out instantly. #JavaScript #EventLoop #WebDevelopment #AsyncJavaScript #TechInterviews

🚀 JavaScript Interview Question You Should Know ❓ What will be the output? console.log(a); var a = 10; console.log(b); let b = 20; 💡 Output: undefined ReferenceError: Cannot access 'b' before initialization 🧠 Explanation: 👉 var a Variables declared with var are hoisted They are initialized with undefined So internally: var a; console.log(a); // undefined a = 10; 👉 let b let is also hoisted BUT… It stays in the Temporal Dead Zone (TDZ) until initialized So accessing it before initialization: console.log(b); // ❌ ReferenceError let b = 20; 🎯 Key Takeaways: ✔ var → hoisted + initialized as undefined ✔ let/const → hoisted but NOT initialized (TDZ) #JavaScript #WebDevelopment #Frontend #CodingInterview #LearnToCode

💡 JS Trick: Infinite Currying This question is often asked in interviews to test your understanding of closures + function chaining. 👉 Infinite currying means calling a function repeatedly like sum(1)(2)(3)(4)... and getting the final result. ✅ How it works: 🔹 Each call stores value using closure 🔹 Returns a function again 🔹 Final value comes when evaluated 🎯 Shortcut to Remember: 👉 Function keeps returning function until final result #JavaScript #CodingInterview #Currying #Closures #Frontend #WebDevelopment #JS

JavaScript developers 👀 What will be the output? var obj = { name: "Guest", welcomeFn: function () { return "Hello " + this.name; } }; var obj2 = { welcomeFn: obj.welcomeFn, name: "User" }; console.log(obj2.welcomeFn()); Looks simple… but many get it wrong 👀 Drop your answer 👇 Explanation coming soon #JavaScript #FrontendDeveloper #InterviewPrep #ReactJS

🚨 React Interview Scenario (Real World) You have a component that fetches data from an API. useEffect(() => { fetchData(); }, []); Everything works fine… But suddenly: 👉 API is called multiple times 👉 Even though dependency array is empty 👀 Why is this happening? 👉 How would you fix it? Bonus: What changes in production vs development? #ReactJS #FrontendInterview #ReactHooks #JavaScript #FrontendDeveloper #WebDevelopment

One of the most common JavaScript interview questions: "Why does setTimeout with 0ms delay not run immediately?" Most developers cannot answer this correctly. Here is the full explanation: JavaScript is single-threaded. It can only do one thing at a time. The Event Loop is how it manages everything else. The execution order is always the same: 1 — Synchronous code runs first All regular code on the Call Stack executes immediately. 2 — Microtasks run second Promises, async/await — these run before anything else once the Call Stack is empty. 3 — Macrotasks run last setTimeout, setInterval, DOM events — these wait until ALL microtasks are done. This is why setTimeout with 0ms still runs after a Promise. The Promise is a microtask. setTimeout is a macrotask. Microtasks always win. Understanding this prevents real bugs in production — async state updates, race conditions, unexpected render order. Save this post for your next async debugging session. Have you ever been confused by JavaScript async order? Drop a comment below. #JavaScript #WebDevelopment #Frontend #SoftwareEngineering #AsyncJavaScript

15 JavaScript interview questions. DOM Manipulation & Events. Answer karo comments mein 👇 DOM Basics Q1. What is the DOM? Q2. What is the difference between querySelector and getElementById? Q3. What is the difference between textContent and innerHTML? Events Q4. What is an event listener and how do you add one? Q5. How do you remove an event listener? Q6. What is event bubbling? Q7. What is the difference between event bubbling and event capturing? Q8. What is e.stopPropagation() and when do you use it? Q9. What is e.preventDefault() and when do you use it? Q10. What is the difference between e.target and e.currentTarget? Event Delegation Q11. What is event delegation and why is it important? Q12. How does React use event delegation internally? Advanced Q13. What are synthetic events in React? Q14. Why should you avoid direct DOM manipulation in React? Q15. What is the difference between mouseenter and mouseover? Full answers + code on GitHub 👇 https://lnkd.in/dj72-XEi #JavaScript #JStoReact #InterviewPrep #WebDevelopment #Frontend #ReactJS #30DayChallenge #JavaScriptTips #FrontendDeveloper #100DaysOfCode

Day 9 – React Interview Journey 🚀 DOM: The Document Object Model is a tree structure of your webpage that browsers use to display and update content. Why Virtual DOM? The Virtual DOM was created to improve performance by minimizing direct updates to the real DOM. 💬 What’s one React concept you struggled with at first? Drop it below 👇 #Day9 #ReactJS #FrontendDevelopment #WebDevelopment #JavaScript #CodingJourney #InterviewPrep