🚀 Top 100 JavaScript Interview Questions

📘 1. JavaScript Fundamentals (1–20)

1. What is JavaScript?

2. What are the different data types in JavaScript?

3. What is the difference between "var", "let", and "const"?

4. What are primitive and non-primitive data types?

5. What is type coercion?

6. What is the difference between "==" and "==="?

7. What are truthy and falsy values?

8. What is "undefined"?

9. What is "null"?

10. What is "NaN"?

11. What is the "typeof" operator?

12. What are template literals?

13. What are JavaScript operators?

14. What are ternary operators?

15. What is variable hoisting?

16. What is scope in JavaScript?

17. What are global, function, and block scope?

18. What is strict mode ("use strict")?

19. What are comments in JavaScript?

20. What are JavaScript modules?

📗 2. Functions & Objects (21–40)

1. What is a function?

2. What is a function expression?

3. What are arrow functions?

4. What is an IIFE (Immediately Invoked Function Expression)?

5. What are callback functions?

6. What are higher-order functions?

7. What are closures?

8. What is lexical scope?

9. What is the "this" keyword?

10. What are object literals?

11. How do you create objects in JavaScript?

12. What is object destructuring?

13. What is the spread operator (...)?

14. What is the rest operator?

15. What are default parameters?

16. What is optional chaining (?.)?

17. What is nullish coalescing (??)?

18. What are object methods?

19. What is method chaining?

20. What is object freezing and sealing?

📙 3. Arrays & ES6+ (41–60)

1. How do arrays work in JavaScript?

2. What is the difference between "map()" and "forEach()"?

3. What is "filter()"?

4. What is "reduce()"?

5. What is "find()"?

6. What is "findIndex()"?

7. What is "some()"?

8. What is "every()"?

9. What is the difference between "slice()" and "splice()"?

10. What are "push()", "pop()", "shift()", and "unshift()"?

11. How do you sort arrays?

12. What is array destructuring?

13. What are Sets?

14. What are Maps?

15. What are Symbols?

16. What are generators?

17. What are iterators?

18. What is destructuring assignment?

19. What is dynamic import?

20. What are ES6 modules?

📕 4. Asynchronous JavaScript (61–80)

1. What is asynchronous programming?

2. What is the event loop?

3. What is the call stack?

4. What is the callback queue?

5. What are Promises?

6. What are the states of a Promise?

7. What is "async/await"?

8. What is "Promise.all()"?

9. What is "Promise.race()"?

10. What is "Promise.allSettled()"?

11. What is "fetch()"?

12. What is AJAX?

13. What are Web APIs?

14. What is "setTimeout()"?

15. What is "setInterval()"?

16. What is "clearTimeout()"?

17. What is "clearInterval()"?

18. What is callback hell?

19. How do you avoid callback hell?

20. What are microtasks and macrotasks?

💡 5. DOM, Browser & Advanced Concepts (81–100)

1. What is the DOM?

2. How do you select DOM elements?

3. What is event bubbling?

4. What is event capturing?

5. What is event delegation?

6. What is the difference between "preventDefault()" and "stopPropagation()"?

87.

What is localStorage?

88. What is sessionStorage?

89. What are cookies?

90. What is debouncing?

91. What is throttling?

92. What is memoization?

93. What is currying?

94. What is prototype inheritance?

95. What is prototypal inheritance?

96. What are classes in JavaScript?

97. What is garbage collection?

98. How does JavaScript manage memory?

99. What are CommonJS and ES Modules?

100. What are the latest JavaScript features introduced in ES2025 and beyond?

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