JavaScript Object Methods

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;
  }

};

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