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How does the this keyword work in JavaScript?
`this` is determined by how a function is called, not where it is written.
Ideal Answer
this refers to the execution context of the current function — specifically, the object that "owns" the call. It is dynamic: determined at call time, not definition time.
| Call site | this value (typical) |
|---|---|
Method call obj.fn() |
obj |
| Plain function (non-strict) | Global object (window / globalThis) |
| Plain function (strict mode) | undefined |
new Constructor() |
Newly created instance |
call / apply / bind |
Explicitly set value |
| Arrow function | Lexically inherited from enclosing scope (no own this) |
JavaScript
const person = {
name: 'Ada',
greet() { return this.name },
greetArrow: () => this?.name // inherits outer `this`, not person
}
person.greet() // "Ada"
const fn = person.greet
fn() // undefined (strict) or global (sloppy)
const bound = person.greet.bind(person)
bound() // "Ada"Arrow functions do not have their own this, arguments, super, or new.target — a frequent source of bugs when passing methods as callbacks.