JavaScript this Keyword Interview Questions 2026: 26 Q&A

Last Updated: June 2026 | Level: Freshers to Mid-Level | Read Time: ~15 min

The this keyword is the single most misunderstood part of JavaScript, which makes it an interview favourite. Candidates report that call-site binding, the call/apply/bind trio, and arrow-function behaviour are guaranteed for frontend roles. This guide covers 26 this questions with full answers and predict-the-output traps. Behaviour reflects the official MDN documentation; confirm any binding nuance on MDN.

Pair this with JavaScript Interview Questions for Freshers 2026 and JavaScript Output Questions 2026.

Table of Contents

1. Binding Rules (Q1 to Q10)
2. call, apply, bind (Q11 to Q17)
3. Arrow Functions (Q18 to Q22)
4. Advanced (Q23 to Q26)
5. Predict the Output
6. Quick Revision Table
7. Frequently Asked Questions

Binding Rules

Q1. What does this refer to in JavaScript? Easy

Q2. What are the rules that determine this? Hard

Q3. What is implicit binding? Medium

const obj = { x: 1, get() { return this.x; } };
obj.get();   // 1, this is obj

Q4. What is default binding? Medium

Q5. What happens to this when a method is detached? Hard

const get = obj.get;
get();   // undefined or error, lost binding

Q6. What is new binding? Medium

Q7. What is this at the top level of a script? Medium

Q8. What is this inside a regular function called normally? Easy

Q9. Does this depend on where a function is defined? Medium

Q10. What is this inside a setTimeout callback? Hard

call, apply, bind

Q11. What does call do? Medium

function greet() { return this.name; }
greet.call({ name: "A" });   // "A"

Q12. What does apply do? Medium

Q13. What does bind do? Medium

const bound = greet.bind({ name: "B" });
bound();   // "B"

Q14. What is the difference between call, apply, and bind? Medium

Q15. Can you override a bound function's this with call? Hard

Q16. What is partial application with bind? Medium

Q17. What does new do to a bound function? Hard

Arrow Functions

Q18. How does this work in an arrow function? Medium

Q19. Why are arrow functions bad as object methods? Medium

Q20. Why are arrow functions good for callbacks? Medium

Q21. Can you change an arrow function's this with call or bind? Hard

Q22. Do arrow functions have their own arguments object? Medium

Advanced

Q23. What is this in a class method? Medium

Q24. How do you preserve this in a React-style event handler? Medium

Q25. What is this in an event listener callback? Hard

Q26. What is the difference between this and self in older code? Medium

Predict the Output

Snippet 1

const obj = {
  name: "A",
  regular() { return this.name; },
  arrow: () => this.name
};
console.log(obj.regular(), obj.arrow());

Output:

A undefined

Why: The regular method binds this to obj. The arrow inherits this from the outer scope (not obj), so this.name is undefined.

Snippet 2

function f() { return this.x; }
const a = f.bind({ x: 1 });
console.log(a.call({ x: 2 }));

Output:

1

Why: Once bound to {x:1}, a later call cannot override the bound this. The bound value wins.

Snippet 3

const obj = {
  vals: [1, 2, 3],
  sum() { return this.vals.reduce((a, b) => a + b, 0); }
};
console.log(obj.sum());

Output:

6

Why: sum is called on obj so this is obj; the arrow callback in reduce does not need this, so it works correctly.

Quick Revision Table

Frequently Asked Questions

What this question is asked most in JavaScript interviews in 2026?

Candidates report that how this is determined by the call site, the difference between call, apply, and bind, and why arrow functions do not have their own this are the three most repeated questions on the this keyword.

Why do arrow functions not have their own this?

Arrow functions inherit this from the enclosing lexical scope at definition time, which makes them ideal for callbacks but unsuitable as object methods that need their own this.

What is the difference between call, apply, and bind?

call and apply invoke a function immediately with an explicit this, call taking arguments individually and apply taking an array. bind returns a new function permanently bound to that this without calling it.

Why does a detached method lose its this?

Because this is set by the call site, and calling a detached method plainly triggers default binding (global object or undefined in strict mode) rather than the original object. Use bind or an arrow wrapper to preserve it.

Can call override a bound function's this?

No. Once bound with bind, the this is fixed and a later call or apply cannot change it. This permanence is by design, though new on a bound function is a documented exception.

Related Articles

• JavaScript Interview Questions for Freshers 2026, the master set
• JavaScript Output Questions 2026, this and binding traps
• JavaScript Closures Interview Questions 2026, scope and closures
• JavaScript Async Await Interview Questions 2026, the event loop

Confirm any binding semantics on the official MDN documentation before your interview. This guide reflects candidate-reported patterns and public preparation resources as of June 2026.