this in global scope in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does this refer to in the global scope in JavaScript?

In the global scope, this refers to the global object. In browsers, this is usually the window object.

intermediate

How does this behave differently in strict mode in the global scope?

In strict mode, this in the global scope is undefined instead of the global object.

intermediate

What is the global object in Node.js when using this in the global scope?

In Node.js, the global object is global, but this in the top-level global scope of a module is not global; it is an empty object {}.

beginner

Code snippet:

console.log(this);

What will this print in a browser's global scope?

It will print the window object, which is the global object in browsers.

beginner

Why is understanding this in the global scope important?

Because it helps you know what object your code is referring to, avoiding bugs and unexpected behavior especially when switching between strict mode and non-strict mode or different environments.

In a browser, what does this refer to in the global scope (non-strict mode)?

A document object

B undefined

C null

D window object

this in the global scope refers to the global object, which is window in browsers.

What is the value of this in the global scope when running JavaScript in strict mode?

A undefined

B window object

C global object

D null

In strict mode, this in the global scope is undefined.

In Node.js modules, what does this refer to at the top-level global scope?

A an empty object

B module.exports

C global object

D undefined

In Node.js modules, this at the top-level is an empty object, not the global object.

Which of the following is true about this in the global scope?

A <code>this</code> always refers to the global object

B <code>this</code> is always undefined

C <code>this</code> can be undefined in strict mode

D <code>this</code> refers to the current function

In strict mode, this in the global scope is undefined; otherwise, it refers to the global object.

What will console.log(this === window); output in a browser's global scope (non-strict mode)?

A false

B true

C undefined

D TypeError

In the browser global scope, this is the window object, so the comparison is true.

Explain what this refers to in the global scope in JavaScript and how strict mode changes it.

Think about what object <code>this</code> points to when you run code outside any function.

Describe how this behaves differently in the global scope between browser and Node.js environments.

Consider the global objects and module system in both environments.