Javascript Object

In JavaScript, an object is a complex data structure that allows you to store collections of key-value pairs. Objects are one of the core components of JavaScript and are used to represent real-world entities, such as a user, a car, or any other item that has properties and behaviors.

OR

Object is used to store multiple values. object has key and value pair.

Characteristics of JavaScript Objects

Key-Value Pairs: Each item in an object is stored as a key-value pair, where the key is a string (or Symbol) that identifies the property, and the value can be any data type (string, number, array, function, etc.).

Properties and Methods: The values associated with keys in an object are called properties if they are data and methods if they are functions.

var obj={name:"John",age:35,sex:"Male"}

You can define multiple objects into the Array. you can say these are Array Object.

var users_details=[{name:"John",age:35,sex:"Male"},
      {name:"Rom",age:30,sex:"Male"},
      {name:"Neena",age:25,sex:"female"}
    ]

   var user_details={
     first_name:"John",
     last_name:"Taylor",
     age:35,
     full_name: function() {
       return this.first_name + " " + this.last_name;
   }

   }

Note:- full_name is a method in the user_details Object.

Suppose you have user_details Object and you want to get the key value

     var user_details={
     first_name:"John",
     last_name:"Taylor",
     age:35,
     full_name: function() {
       return this.first_name + " " + this.last_name;
   }

   }

Example:- get the user’s full_name and age.

console.log(user_details.full_name);

get the age of the user

console.log(user_details.age);

Suppose you have user_details Object

 var user_details={
     first_name:"John",
     last_name:"Taylor",
     age:35
   }

Now, you want to add user_id into the user_details Object

 user_details.user_id=1234

Now get the user_details value

console.log(user_details);

Try it Yourself

Suppose you have user_details Object

var user_details={
     first_name:"John",
     last_name:"Taylor",
     age:35
   }

Now, you have to update age into the user_details Object

 user_details.age=36

Now get the user_details value

console.log(user_details);

Syntax:-

delete object.key

Example:- delete the age key value from the Object

     var user_details={
     first_name:"John",
     last_name:"Taylor",
     age:35
   }

   delete user_details.age;

   console.log(user_details);

Try it Yourself

Syntax:- get the Object value

for (var key in Object){
	
 console.log(Object[key]);

}

Example:- Suppose you have users object.

let users={
	id:1,
	first_name:"John",
	last_name:"Taylor",
	age:35
}

Get the users object value

for (var key in users){
	
	console.log(users[key]);

}

Try it Yourself

Syntax:-

object_name.hasOwnProperty(object_key);  //Output true or false

Example:- Suppose you have users object.

let users={
	id:1,
	first_name:"John",
	last_name:"Taylor",
	age:35
}

Now check the key is exists or not

users.hasOwnProperty("first_name");  //Output true

users.hasOwnProperty("email");  //Output false

Try it Yourself

Syntax:-

Object.keys(object_name);  

Example:- Suppose you have users object.

let users={
	id:1,
	first_name:"John",
	last_name:"Taylor",
	age:35
}

Now you want the all users object keys

Object.keys(users);  

Try it Yourself

Syntax:-

Object.values(object_name);  

Example:- Suppose you have users object.

let users={
	id:1,
	first_name:"John",
	last_name:"Taylor",
	age:35
}

Now you want the all users object values

Object.values(users);  

Try it Yourself

Javascript Object – Interview Questions

Javascript Object – Objective Questions (MCQs)