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JavaScript Objects

Objects in JavaScript

The objects in JavaScript is a structure that has a state and behavior or we can say properties or method just like, Bike, pen, car, etc.
It is a known fact that JavaScript is an object-based language and every single thing in JavaScript is called an Object.

In JavaScript, class is not created in order to get the object instead, the object is created directly hence, making it a template-based language.

These three ways are followed to create objects in JavaScript:

  • Object Literal
  • Object Directly (using new keyword)
  • Object Constructor (using new keyword)

1. Object by Object literal in JavaScript

Here is the syntax for creating object by Object Literal:

object={property1:value1,property2:value2.....propertyN:valueN}  

Please note that the property and value is separated by : (colon).

Let's understand this method of object creation by this simple example:

<script>
emp={id:101,name:"Radhe Shyam",salary:120000}  
document.write(emp.id+" "+emp.name+" "+emp.salary);   
</script>
Output :

The output of the above mentioned example is: 101 Radhe Shyam 120000

2. Object by Object directly

Here is the syntax of creating object directly:

var objectname=new Object();   

Please note that new keyword is used here to create object.

Let's understand the object directly with this example:

<script>
var emp=new Object();  
emp.id=130;  
emp.name="Hello Employee";  
emp.salary=90000;  
document.write(emp.id+" "+emp.name+" "+emp.salary);     
</script>
Output :

The output of the above mentioned example is: 130 Hello Employee 90000

3. Object Constructor in JavaScript

In this method functions needs to be created with arguments and each argument value can be assigned easily in the current object by the help of this keyword. Please note that ‘this’ keyword is referring to the current object.

Here is an example to understand this easily:

var objectname=new Object();   

Please note that new keyword is used here to create object.

Let's understand the object directly with this example:

<script>
function emp(id,name,salary){  
this.id=id;  
this.name=name;  
this.salary=salary;  
}  
e=new emp(11,"hello hi",65000);    
document.write(e.id+" "+e.name+" "+e.salary);       
</script>
Output :

The output of the above mentioned example is: 11 hello hi 65000

Let's Understand The Defining Method In Javascript

A method can be defined in JavaScript Object but in order to define method a property needs to be added in the function with the same name as of method. Here is an example to explain it better:

<script>
function emp(id,name,salary){  
this.id=id;  
this.name=name;  
this.salary=salary;    
this.changeSalary=changeSalary;  
function changeSalary(otherSalary){  
this.salary=otherSalary;  
}  
}  
e=new emp(10,"oonu aiwal",5000);  
document.write(e.id+" "+e.name+" "+e.salary);  
e.changeSalary(56000);  
document.write("
"+e.id+" "+e.name+" "+e.salary);        
</script>
Output :

The output for the above mentioned example is:
10 oonu aiwal 5000
10 oonu aiwal 56000

Object Methods in JavaScript

Here are the following various object methods in JavaScript:

Methods Description
Object.assign() This method copies own properties from a source object to a target object
Object.create() It is used to create a new object with the specified prototype object and properties
Object.defineProperty() It is used to describe some behavioral attributes of the property
Object.defineProperties() It is used to create or configure multiple object properties
Object.entries() It returns an array with arrays of the key, value pairs
Object.freeze() It prevents existing properties from being removed
Object.getOwnPropertyDescriptor() It returns a property descriptor for a specified property of a specified object
Object.getOwnPropertyDescriptors() It returns all own property descriptors of a given object
Object.getOwnPropertyNames() It returns an array of all properties (enumerable or not) found
Object.getOwnPropertySymbols() It returns an array of all own symbol key properties
Object.getPrototypeOf() It returns the prototype of the specified object
Object.is() It determines whether two values are the same value
Object.isExtensible() It determines if an object is extensible
Object.isFrozen() It determines if an object was frozen
Object.isSealed() It determines if an object is sealed
Object.keys() It returns an array of a given object's own property names
Object.preventExtensions() It is used to prevent any extensions of an object
Object.seal() It prevents new properties from being added and marks all existing properties as non-configurable
Object.setPrototypeOf() It sets the prototype of a specified object to another object
Object.values() It returns an array of values