Top 25 Programming Interview Questions for JavaScript Developers

Here the list of top programming #interview questions: Get all 232 ques & ans for free on interviewdepth.com 1. Reverse a String 2. Check if a String is a Palindrome 3. Remove Duplicates from a String 4. Find the First Non-Repeating Character 5. Count the Occurrences of Each Character 6. Reverse Words in a Sentence 7. Check if Two Strings are Anagrams 8. Find the Longest Substring Without Repeating Characters 9. Convert a String to an Integer (atoi Implementation) 10. Compress a String (Run-Length Encoding) 11. Find the Most Frequent Character 12. Find All Substrings of a Given String 13. Check if a String is a Rotation of Another String 14. Remove All White Spaces from a String 15. Check if a String is a Valid Shuffle of Two Strings 16. Convert a String to Title Case 17. Find the Longest Common Prefix 18. Convert a String to a Character Array 19. Replace Spaces with %20 (URL Encoding) 20. Convert a Sentence into an Acronym 21. Check if a String Contains Only Digits 22. Find the Number of Words in a String 23. Remove a Given Character from a String 24. Find the Shortest Word in a String 25. Find the Longest Palindromic Substring #javascript #javascriptdeveloper #reactjs #reactnative #vuejsdeveloper #angular #angulardeveloper

📝 JavaScript Interview Coding Task Question – Day 73 Look at this code snippet 👇 ✅ Answer & Explanation: Parent constructor Child constructor Hello from Parent Hello from Child 1️⃣ The super keyword in classes is used to call methods on the parent class. 2️⃣ In the Child class, the constructor calls super() → this triggers the Parent constructor first before accessing this. 3️⃣ When child.sayHello() is called, it uses the overridden method in Child, but inside it, super.sayHello() invokes the parent’s version. 4️⃣ The output shows how inheritance chains both constructors and methods, combining parent and child logic. ✨ Tip: 👉 Always call super() before using this in a subclass constructor. 👉 super.method() helps reuse parent logic without rewriting it. #100DaysOfCode #JavaScript #Frontend #WebDevelopment #CodingInterview #JSClasses #Inheritance #DailyCoding #LearnInPublic #kirantechnophile

learn the top 20 javascript concepts every developer must master All explained simply and practically in this tutorial. From hoisting and closures to async/await, event loop, and prototypes, this guide covers everything you need to build a strong foundation in javascript. each concept is explained with key points, making it perfect for beginners, frontend developers, and anyone preparing for javascript interviews. . . . . 📘 what’s inside: ~hoisting and execution context ~this keyword and lexical scope ~promises & async/await ~prototypes & inheritance ~memory management & event loop ~debounce & throttle functions ~destructuring, spread, and rest operators . . . . . . . #javascript #javascripttutorial #learnjavascript #frontenddeveloper #webdevelopment #programming #coding #developerlife #webdeveloper #frontenddevelopment #reactjs #nodejs #webdesign #softwaredevelopment #codingforbeginners #learncoding #javascriptconcepts #asyncawait #closures #eventloop

## 🚀 **Top 10 JavaScript Concepts Every Developer Should Know!** 💛 JavaScript is the heart of web development — mastering its core concepts makes you a real problem-solver! Let’s quickly revisit some powerful fundamentals 👇 --- ### 🧩 1️⃣ **Variables (`var`, `let`, `const`)** * `var` → Function-scoped * `let`, `const` → Block-scoped * Use `const` when the value won’t change. ```js let name = "Vijaya"; const age = 25; ``` --- ### ⚡ 2️⃣ **Hoisting** Variables and functions are moved to the top of their scope before execution. ```js console.log(x); // undefined var x = 5; ``` --- ### 🌀 3️⃣ **Closures** A function “remembers” the variables from its parent scope — even after the parent is gone! ```js function outer() { let count = 0; return function inner() { count++; console.log(count); }; } const counter = outer(); counter(); // 1 counter(); // 2 ``` --- ### 🧠 4️⃣ **Promises & Async/Await** Handle asynchronous code neatly. ```js async function getData() { const data = await fetch('https://api.example.com'); console.log('Data loaded!'); } ``` --- ### 🧮 5️⃣ **Array Methods** Powerful one-liners for clean code: * `map()` – transform data * `filter()` – filter elements * `reduce()` – combine values ```js let nums = [1,2,3]; let doubled = nums.map(n => n*2); ``` --- ### 🔁 6️⃣ **Callback Functions** A function passed as an argument to another function. ```js function greet(name, callback) { callback(`Hello ${name}`); } greet("Vijaya", console.log); ``` --- ### 🧱 7️⃣ **Objects & Destructuring** Extract values easily: ```js const user = {name: "Vijaya", age: 22}; const {name, age} = user; ``` --- ### 🔥 8️⃣ **ES6 Features** Modern JavaScript = cleaner syntax! ✅ Template literals ✅ Arrow functions ✅ Spread & Rest operators ✅ Modules ```js const arr = [1, 2]; const newArr = [...arr, 3]; ``` --- ### 🧭 9️⃣ **Event Loop** JS is single-threaded but handles async tasks smartly. 📚 Tasks go to the callback queue and execute when the main thread is free. --- ### 💥 🔟 **DOM Manipulation** Make your webpage dynamic! ```js document.getElementById("demo").innerText = "Hello JS!"; ``` --- ### ✨ **Final Thought** > “Knowing syntax is easy — understanding concepts makes you a real developer.” Keep practicing, keep building 💪 #JavaScript #WebDevelopment #CodingJourney #LearnWithMe #FrontendDeveloper #LinkedInLearning #100DaysOfCode Ajay Babu Sappa 10000 Coders sanjeev ch Manivardhan Jakka

📝 JavaScript Interview Coding Task Question – Day 72 Look at this code snippet 👇 ✅ Answer & Explanation: 1️⃣ Object.create(proto) creates a new object whose prototype is proto. It does not call a constructor function. 2️⃣ So child.name → "Kiran" because JavaScript looks up the prototype chain (since child doesn’t have its own name). 3️⃣ After setting child.name = "Sai", the name property is now created on child itself — it shadows the prototype’s property. 4️⃣ proto.name remains "Kiran", proving that child and proto are independent objects connected by prototype inheritance. ✨ Tip: 👉 Object.create() is great for lightweight inheritance without constructors. 👉 Property lookups follow the prototype chain, but assignments always go to the current object unless explicitly modified on the prototype. #100DaysOfCode #JavaScript #Frontend #WebDevelopment #CodingInterview #JSChallenges #LearnInPublic #DailyCoding #kirantechnophile

Thinking Beyond the Code:- Anyone can learn to write code. But not everyone learns to understand what they’re building. Real developers don’t just chase syntax — they chase purpose, logic, and clarity. Every function, every component, every pixel — it all connects to a bigger picture. Because writing code is easy. But building something meaningful? That takes vision. #DeveloperMindset #FrontendDeveloper #CodeWisely #JavaScript #WebDevelopment #KeepLearning #BuildWithPurpose

🚀 Master JavaScript Variable Naming — Made Simple! Clean and consistent naming is one of the most underrated skills in JavaScript. A well-named variable improves readability, reduces bugs, and makes your code easier for everyone on the team to understand. Here are the 5 essential naming rules every JavaScript developer should follow: 🔹 Must start with a letter, _, or $ 🔹 Can contain letters, digits, and $ 🔹 No spaces in variable names 🔹 Cannot use reserved words (like let, if, const) 🔹 Use descriptive names and follow camelCase Good naming = clean code = better developer experience ✨ 💬 What naming conventions do you follow in your projects? #JavaScript #JavaScriptTips #CleanCode #CodingTips #ProgrammingBasics #WebDevelopment #FrontendDeveloper #FullStackDeveloper #SoftwareEngineering #CodeQuality #DeveloperProductivity #JavaScriptDevelopment #LearnToCode #ProgrammingLife #WebDevCommunity #FrontendTips #SoftwareBestPractices #CodingStandards #TechEducation #ProblemSolving #SoftwareDeveloper #TechSkills #CodingJourney #DeveloperExperience #DevCommunity #ProgrammingFundamentals #JSDeveloper #ModernJavaScript #WebDeveloper #python #PythonFullStack

This tiny newline can break your JavaScript code😱 #coding #javascript #frontend This JavaScript short explains one of the most confusing return statement bugs caused by Automatic Semicolon Insertion (ASI). Learn why the same-looking functions return different results — and how to avoid this hidden trap in your code. Perfect for JavaScript interviews, beginners, and advanced devs who want to understand JS deeply. #JavaScript #CodingShorts #JSInterview #TheDeveloperSchool #JavaScript #CodingShorts #TheDeveloperSchool #WebDevelopment #JSInterview #FrontendDeveloper #FullStackDeveloper #JavaScriptTips #LearnCoding #CodeShorts #ProgrammingShorts #TechInterview

🚀 Day 4 of my 4 Days – 4 JavaScript Questions Challenge! Once in a while, you’ll face this classic interview question: 💭 "What is a Prototype in JavaScript?" I remember the first time I was asked this — I completely blanked out 😅 But you don’t have to! Here’s how you can confidently explain it in your next interview 👇 In JavaScript, every function automatically gets a prototype property, which is an empty object by default. This prototype object is used to add properties and methods that can be shared across all instances created by that function (when used as a constructor with new). function Person(name) {  this.name = name; } // Adding a method to prototype Person.prototype.greet = function() {  console.log("Hello, " + this.name); }; const user1 = new Person("Anurag"); const user2 = new Person("Sachin"); user1.greet(); // Hello, Anurag user2.greet(); // Hello, Sachin Both objects share the same method via the prototype — making it memory-efficient and powerful. 💪 #JavaScript #FrontendDevelopment #WebDevelopment #JSChallenge #LearningByCoding #UIDeveloper #TechJourney #CodingCommunity

🚀 Writing Cleaner and Smarter JavaScript In interviews, solving a problem is important — but showing clean, efficient code can leave an even stronger impression. Here’s a simple example: checking whether a number is even or odd. ✨ These small optimizations show clarity, intent, and modern JavaScript thinking. Sometimes the simplest tasks reveal the most about a developer’s mindset. 💡 Write clean. Think smart. Keep improving. #javascript #coding #programming #Reactjs #nodejs #interview