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Learn/JavaScript/Objects, Classes, and Advanced Patterns
JavaScript•Objects, Classes, and Advanced Patterns

JavaScript Object Methods

Concept visual

JavaScript Object Methods

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Start at both ends

What are Object Methods?

Methods are actions that can be performed on objects. Methods are functions stored as property values.

Example

const person
= {
firstName: "John", lastName: "Doe", age: 50, fullName: function() {
return this.firstName + " " +
this.lastName;
}
};

Property

Value firstName

John lastName

Doe age

50 fullName function()

{
return this.firstName + " "  + this.lastName;
}

The this

Keyword

In an object method, this refers to the object.

Example 1 const person = {
firstName: "John", lastName: "Doe", id: 5566, getId: function() {
return this.id;
}
};
let number = person.getId();

In the example above, this refers to the person object. this.id means the id property of the person object.

Example 2 const person

= {
firstName: "John", lastName: "Doe", age: 50, fullName: function() {
return this.firstName + " " +
this.lastName;
}
};

In the example above, this refers to the person object. this.firstName means the firstName property of the person object. this.lastName means the lastName property of the person object.

Accessing Object Methods

To call an object method, add parentheses ()

Without parentheses you get the function itself. Syntax objectName.methodName () If you call a method with parentheses, it will execute as a function

Example name = person.fullName();

If you call a method without parentheses, it will return the function definition

Example name = person.fullName;

Adding a Method to an Object

You can add a method to an object by assigning a function to a property

Example

// Assign person.name to a function person.name = function () {
return this.firstName + " " + this.lastName;
};

In the example above, person.name is a property with a function assigned to it.

Adding a JavaScript Method

This example uses the JavaScript toUpperCase()

method to convert a text to uppercase:

Example person.name = function () {
return (this.firstName + " " + this.lastName).toUpperCase();
};

Summary

Methods are functions stored as object properties

Call a method with parentheses:

person.fullName() In methods, this refers to the object You can add methods to objects by assigning a function to a property

See Also:

What are JavaScript Objects?

What are Object Properties?

What is this in Objects?

How to Display JavaScript Objects

What is an Object Constructor?

Advanced Chapters:

Previous

JavaScript Callbacks

Next

JavaScript Temporal Duration