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this
1. Explain the 5 rules that determine the value of this in JavaScript. Walk through each with an example.
Level: Expert | Frequency: High
2. What is the default binding of this? How does strict mode change it?
Level: Expert | Frequency: High
3. What is the difference between implicit and explicit binding? When does implicit binding get lost?
Level: Expert | Frequency: High
4. How does this behave differently in arrow functions vs regular functions? Why?
Level: Expert | Frequency: High
5. What does new binding do to this? What happens internally when you use new?
Level: Expert | Frequency: High
6. Can this inside an arrow function be changed using .call(), .apply(), or .bind()? Why or why not?
Level: Expert | Frequency: High
7. What is the value of this in a class constructor? What about in a class method called as a callback?
Level: Expert | Frequency: High
8. What is the difference between call, apply, and bind? When would you use each?
Level: Expert | Frequency: High
9. Explain how this works in event listeners. How do you preserve the correct this when using class methods as event handlers?
Level: Expert | Frequency: High
10. How does this behave in a module (ESM) at the top level vs CommonJS?
Level: Expert | Frequency: High
11. What is 'context loss' and what are the three most common ways to fix it in production code?
Level: Expert | Frequency: High
12. How does Function.prototype.bind work under the hood? Can you implement a polyfill for it?
Level: Expert | Frequency: High
13. How does this behave in prototype chain method calls? Does it refer to the instance or the prototype?
Level: Expert | Frequency: High
14. When mixing ES6 classes with prototype manipulation, how can this become unpredictable?
Level: Expert | Frequency: High
15. How do React class components use this, and why did binding in the constructor become a common pattern? How did arrow function class fields solve it?
Level: Expert | Frequency: High
16. In what real-world scenarios have you encountered this-related bugs? How did you debug and fix them?
Level: Expert | Frequency: High
17. What are the trade-offs between using arrow functions everywhere to avoid this confusion vs using regular functions with explicit binding?
Level: Expert | Frequency: High
18. How would you explain the this keyword to a junior developer in one analogy?
Level: Expert | Frequency: High
19. Can you think of a scenario where using .bind() causes a memory issue? How would you address it?
Level: Expert | Frequency: High
All Topics
Basics
Engine
JIT
V8
Event Loop and Runtime
Concurrency and Threading
Bytecode and Parsing
Execution Context
Data Types
Functions
String Operations
Array Operations
this
Call Apply Bind
Closure
Objects
ES6 Classes
Events
ES6
Promises
Iterator and Generator
Error Handling
Web Workers
PWA
Web Sockets
Web Assembly
Garbage Collector
Modules
Browser APIS
Functional Programming
Currying
Higher Order Functions
Memoisation
Security
Code
Polyfills