What are Objects in Javascript ? – Code Samples

1

Wrote this article on Objects & Javascript for future reference. Codecademy.org is my favorite go-to-place for learning Javascript.

Javascript Objects could be defined in following three manners.

  • Objects created as Variables
  • Objects created using new Object()
  • Objects created using Constructor

 

Objects created as Variables
// Defining object as a variable
var School = {
    name: "DAV Public School",
    studentsCount: 600,
    admissionOpen: false,
};

School.isAdmissionOpen = function() {
    return this.admissionOpen;
};

School.setAdmissionStatus = function( openOrClosed ) {
    this.admissionOpen = openOrClosed;
};

 

Objects created using new Object()

In the example below, College is an object type.

// Creating object using new Object()  
var College = new Object();
College.name = "IIT Kharagpur";
College.strength = 3500;
College.admissionStatus = false;
College.isAdmissionOpen = function() {
    return this.admissionStatus;
}
College.setAdmissionStatus = function( status ) {
    this.admissionStatus = status;
}

 

Objects created using Constructor

In the example below, EducationalInstitution is created using the constructor which implies that different types of educational institutions such as schools, and colleges could be created using this type, EducationalInstitution. The object types are created using new operator such as that shown in the code below. This is unlike previous two cases which can be used to create specific objects.

Also, pay attention to the “prototype” keyword which ensures that the methods such as isAdmissionOpen and setAdmissionStatus can be called on all objects types created using “new EducationalInstitution”. If “prototype” is not used, method defined on one object type could not be called on other object types created using “new EducationalInstitution”.

“Prototype” is also used to implement inheritance.

// Creating Object using Constructor  
function EducationalInstitution( name, strength ) {
    this.name = name;
    this.strength = strength;
    var admissionStatus = false;
}

EducationalInstitution.prototype.isAdmissionOpen = function() {
    return this.admissionStatus;
}

EducationalInstitution.prototype.setAdmissionStatus = function( status ) {
    this.admissionStatus = status;
}

var davPublicSchool = new EducationalInstitution( "DAV Public School", 600 );
davPublicSchool.setAdmissionStatus( true );

var iitKharagpur = new EducationalInstitution( "IIT Kharagpur", 3500 );
iitKharagpur.setAdmissionStatus( false );

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Ajitesh Kumar

Ajitesh Kumar

Ajitesh has been recently working in the area of AI and machine learning. Currently, his research area includes Safe & Quality AI. In addition, he is also passionate about various different technologies including programming languages such as Java/JEE, Javascript and technologies such as Blockchain, mobile computing, cloud-native technologies, application security, cloud computing platforms, big data etc.

He has also authored the book, Building Web Apps with Spring 5 and Angular.
Ajitesh Kumar

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  1. Pingback: Javascript Unit Testing using Jasmine - Code Examples - Bytes Cravings

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