Example #
var person = {
firstName: "John",
lastName : "Doe",
id : 5566,
fullName : function() {
return this.firstName + " " + this.lastName;
}
}; What is this? #
The JavaScript this keyword refers to the object it belongs to.
It has different values depending on where it is used:
- In a method,
thisrefers to the owner object. - Alone,
thisrefers to the global object. - In a function,
thisrefers to the global object. - In a function, in strict mode,
thisisundefined. - In an event,
thisrefers to the element that received the event. - Methods like
call(), andapply()can referthisto any object.
this in a Method #
In an object method, this refers to the “owner” of the method.
In the example on the top of this page, this refers to the person object.
The person object is the owner of the fullName method.
fullName : function() {
return this.firstName + " " + this.lastName;
} var x = this; In strict mode, when used alone, this also refers to the Global object [object Window]:
Example #
"use strict";
var x = this; function myFunction() {
return this;
} "use strict";
function myFunction() {
return this;
}
<button onclick="this.style.display='none'">
Click to Remove Me!
</button> var person = {
firstName : "John",
lastName : "Doe",
id : 5566,
myFunction : function() {
return this;
}
}; Example #
var person = {
firstName: "John",
lastName : "Doe",
id : 5566,
fullName : function() {
return this.firstName + " " + this.lastName;
}
}; In other words: this.firstName means the firstName property of this (person) object.
Explicit Function Binding #
The call() and apply() methods are predefined JavaScript methods.
They can both be used to call an object method with another object as argument.
You can read more about call() and apply() later in this tutorial.
In the example below, when calling person1.fullName with person2 as argument, this will refer to person2, even if it is a method of person1:
Example #
var person1 = {
fullName: function() {
return this.firstName + " " + this.lastName;
}
}
var person2 = {
firstName:"John",
lastName: "Doe",
}
person1.fullName.call(person2); // Will return "John Doe"
