JavaScript Function Reference
Function Object Methods & Properties
Revised December 2025
| Name | Description |
|---|---|
| apply() | Calls a function with a specified this
value and an array of arguments |
| bind() | Returns a function with a specified this value |
| call() | Calls a function with a specified this
value and individual arguments |
| length | Returns the number of (expected) parameters of a function |
| name | Returns the name of the function |
| toString() | Returns a string representation of the function's source. |
What is this?
In JavaScript, the this keyword refers to an object.
The this keyword refers to different objects depending on how it is used:
Alone, this refers to the global object. |
In a function, this refers to the global object. |
In a function, in strict mode, this is undefined. |
In an object method, this refers to the object. |
In an event, this refers to the element that received the event. |
In methods like call(), apply()
and bind(), this can refer to any object. |
this is not a variable.
this is a keyword.
You cannot change the value of this.
This Precedence
Use the following precedence of order to determine which object this refers to:
| Order | Object | Because |
|---|---|---|
| 1 | bind() | this is in a function being called using bind() |
| 2 | apply() | this is in a function being called using apply() |
| 2 | call() | this is in a function being called using call() |
| 3 | Object method | this is in an object function (method) |
| 4 | Global scope | this is in a function in the global scope |
this Precedence
Use the following precedence of order to determine which object
this refers to:
| Order | Object | Because |
|---|---|---|
| 1 | bind() | this is in a function being called using bind() |
| 2 | apply() | this is in a function being called using apply() |
| 2 | call() | this in is a function being called using call() |
| 3 | Object method | this in is an object function (method) |
| 4 | Global scope | this in isa function in the global scope |
