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JavaScript Object Methods


JavaScript Methods

JavaScript methods are the actions that can be performed on objects.

A JavaScript method is a property containing a function definition.

Property Value
firstName John
lastName Doe
age 50
eyeColor blue
fullName function() {return this.firstName + " " + this.lastName;}

Methods are functions stored as object properties.


Accessing Object Methods

You create an object method with the following syntax:

methodName : function() { code lines }

You access an object method with the following syntax:

objectName.methodName()

You will typically describe fullName() as a method of the person object, and fullName as a property.

The fullName property will execute (as a function) when it is invoked with ().

This example accesses the fullName() method of a person object:

Example

name = person.fullName();
Try it Yourself »

If you access the fullName property, without (), it will return the function definition:

Example

name = person.fullName;
Try it Yourself »

Using Built-In Methods

This example uses the toUpperCase() method of the String object, to convert a text to uppercase:

var message = "Hello world!";
var x = message.toUpperCase();

The value of x, after execution of the code above will be:

HELLO WORLD!

Adding New Methods

Adding methods to an object is done inside the constructor function:

Example

function person(firstName, lastName, age, eyeColor) {
    this.firstName = firstName; 
    this.lastName = lastName;
    this.age = age;
    this.eyeColor = eyeColor;
    this.changeName = function (name) {
        this.lastName = name;
    };
}

The changeName() function assigns the value of name to the person's lastName property.

Now You Can Try:

myMother.changeName("Doe");
Try it Yourself »

JavaScript knows which person you are talking about by "substituting" this with myMother.