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Top 50 JavaScript Interview Questions and Answers Master the most frequently asked JavaScript interview questions covering Closures, Hoisting, Scope, Variables, and Core JavaScript Fundamentals. JavaScript Fundamentals 1. What is JavaScript? JavaScript is a high-level, single-threaded, interpreted programming language used to build dynamic and interactive web applications. 2. What are the primitive data types in JavaScript? String Number Boolean Undefined Null Symbol BigInt 3. What is the difference between null and undefined? undefined means a variable has been declared but not assigned a value. null represents an intentional absence of value. 4. Difference between == and ===? == performs type coercion before comparison. === compares both value and datatype. "10" == 10 // true "10" === 10 // false 5. What is NaN? NaN stands for Not a Number and represents an invalid numerical result. Number("Hel...

  Async JavaScript Without Confusion Async JavaScript is one of the biggest turning points in a developer’s journey. This is where JavaScript starts feeling less like simple scripting and more like a real programming language powering modern applications. Loading APIs, waiting for user actions, showing timers, handling notifications, processing payments, updating chats — modern applications constantly deal with asynchronous behavior. And honestly, this is exactly where many beginners get lost. Questions start appearing quickly: Why does JavaScript not wait? How does setTimeout actually work? What is asynchronous behavior? Why were Promises introduced? What happens behind the scenes? The good news? Async JavaScript becomes much easier once you understand the flow properly instead of memorizing syntax blindly. In this guide, you will learn: What asynchronous JavaScript means How setTimeout works How setInterval works What Promises are Basic as...