snippetjavascriptTip

Understanding the "this" keyword in JavaScript

Submitted by: @import:30-seconds-of-code·Mar 2, 2026·

Viewed 0 times

keywordjavascriptunderstandingthisthe

Problem

In JavaScript, the this keyword refers to the object that is currently executing the code. The short version of what this evaluates to is as follows:

By default, this refers to the global object.
In a function, when not in strict mode, this refers to the global object.
In a function, when in strict mode, this is undefined.
In an arrow function, this retains the value of the enclosing lexical context's this.

Solution

console.log(this === window); // true

In a function, when not in strict mode, this refers to the global object.
In a function, when in strict mode, this is undefined.
In an arrow function, this retains the value of the enclosing lexical context's this.
In an object method, this refers to the object the method was called on.
In a constructor call, this is bound to the new object being constructed.
In an event handler, this is bound to the element on which the listener is placed.

Code Snippets

console.log(this === window); // true

function f() {
  return this;
}

console.log(f() === window); // true

'use strict';

function f() {
  return this;
}

console.log(f()); // undefined

Context

From 30-seconds-of-code: this

Revisions (0)

No revisions yet.