Top 50 JavaScript Interview Questions and Answers for 2026
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...