this in objects in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does this refer to inside a regular object method?

this refers to the object that owns the method. It points to the object before the dot when the method is called.

beginner

How does this behave inside a function called without an object?

In non-strict mode, this refers to the global object (like window in browsers). In strict mode, this is undefined.

intermediate

What happens to this when using arrow functions inside objects?

Arrow functions do not have their own this. They inherit this from the surrounding code where they are defined.

intermediate

How can you explicitly set this when calling a function?

You can use call(), apply(), or bind() methods to set this explicitly.

intermediate

What is a common mistake when using this inside callbacks in objects?

Callbacks often lose the original this context because they are called as regular functions. Using arrow functions or binding this fixes this.

Inside an object method, what does this refer to?

A The function itself

B The global object

C Undefined

D The object owning the method

this inside an object method points to the object that owns the method.

What does this refer to inside an arrow function defined in an object?

A The object itself

B The global object

C The surrounding context's <code>this</code>

D Undefined

Arrow functions inherit this from their surrounding context, not from the object.

Which method can you use to explicitly set this when calling a function?

A set()

B call()

C run()

D execute()

call() lets you specify what this should be inside the function.

What happens if you call a regular function (not a method) in strict mode without setting this?

A <code>this</code> is undefined

B <code>this</code> is the function itself

C <code>this</code> is the global object

D <code>this</code> is the object

In strict mode, this is undefined in a regular function call without an object.

Why might this lose its expected value inside a callback function?

A Because callbacks are called as regular functions, losing the original <code>this</code>

B Because callbacks always use global <code>this</code>

C Because <code>this</code> is always undefined in callbacks

D Because callbacks cannot access <code>this</code>

Callbacks are often called as regular functions, so this does not point to the original object unless handled.

Explain how this works inside an object method and how it differs in arrow functions inside objects.

Think about how the function is called and where arrow functions get their this.

Describe ways to control or change the value of this when calling functions in JavaScript.

Remember the three methods that let you set this explicitly.