Understanding Objects in JavaScript

Intro

Some times we need to store related information together. For example we represent a person, we might need his Name, Age, Address. When we use single variable for each, It will be Massy quickly.

let name = "Rahul";
let age = 26;
let address = "Garia, Kolkata"
// so on

Here Object become very helpful in JavaScript.

Objects allow us to store multiple related values inside a single structure using key–value pairs.

What Objects Are and Why They Are Needed

In simple word Object is a collection of key-value pairs.

• key is the name of the property.

• value is those data that we wants store in

Example

let person = {
  name: "Rahul",
  age: 25,
  city: "Kolkata"
};

Here

name is a key and the value is Rahul

age is a key and the value is 25

and also, city is the key and the value is Kolkata

So, the object of a person is the all related information stored in a single structure, very clean and organized.

Creating Objects

There is a multiple ways to create an Object, But the most common way is object literal syntax.

That is pointed the value of a variable, enclosed with a curly braces.

Example

let person = {
  name: "Rahul",
  age: 25,
  city: "Kolkata"
};

Rules:

• Objects use curly braces {}

• Properties are separated by commas

• Each property has a key and value

Accessing Properties

We can access any objects property with two way

1. Dot Notation

This is the most common and simplest method.

let person = {
  name: "Rahul",
  age: 25,
  city: "Kolkata"
};

console.log(person.name) // Rahul
console.log(person.age) // 25

Here we access the property using:

object.property

1. Bracket Notation

We can also use square bracket to access the objects property, basically this method used when the properties are need to access dynamically.

Example

let person = {
  name: "Rahul",
  age: 25,
  city: "Kolkata"
};

console.log(person["name"]) // Rahul

Here we must use the property as a string

Updating Object Properties

Here everything is ok, until we need to change the value of any object property. What about if we need change them?

Don't worry, JavaScript give the that flexibility. Suppose i have assign the age with wrong information, then we can change the data as mentioned bellow

Example

  let person = {
  name: "Rahul",
  age: 25,
  city: "Kolkata"
};

person.age=26

console.log(person.age) // 26

That's easy, JavaScript simply replaces the old value with the new one. Now the output of the age will be 26

Adding New Properties

In such similar ways we can create any un-declared property.

Example

  let person = {
  name: "Rahul",
  age: 25,
};

person.city="Kolkata"

console.log(person) // { name: 'Rahul', age: 25, city: 'Kolkata' }

Deleting Properties

JavaScript give us a default keyword delete by using it we can delete any object's property.

Example

  let person = {
  name: "Rahul",
  age: 25,
  city: "Kolkata"
};

delete person.city

console.log(person) // { name: 'Rahul', age: 25 }

Looping Through Object Keys

Objects are often used with loops to access all properties.

One common way is using for...in loop.

Example

let person = {
    name: "Rahul",
    age: 25,
    city: "Kolkata"
};

for (let key in person) {
    console.log(key + ` = ` + person[key]);
}

Output ->

name = Rahul
age = 25
city = Kolkata

• key represents the property name

• person[key] gives the value

Array vs Object

Arrays store values using index numbers.

let fruits = ["Apple", "Banana", "Orange"];

console.log(fruits[0]); // Apple

0 -> Apple

1 -> Banana

2 -> Orange

But Objects store the value using named keys as a key-values pair

let person = {
  name: "Rahul",
  age: 25
};

console.log(person.name); // Rahul

Array is ordered list, Object is named properties.

Array is access with index numbers (0 - less than own length), Object access with key name.

Array Simple can be a list of items, we can use Object as a information storage.

Let's play with Object

1. Create an object representing a student

let student = {
name: "Janardan",
age: 26,
course: "Cohort2025"
}

1. Update one property

let student = {
name: "Janardan",
age: 26,
course: "Cohort2025"
}

student.course = "Cohort2026"

1. Print all keys and values using a loop

let student = {
    name: "Janardan",
    age: 26,
    course: "Cohort2025"
}

student.course = "Cohort2026"

for (const key in student) {
    console.log(`\({key} : \){student[key]}`);
}

Output ->

name : Janardan
age : 26
course : Cohort2026

Thank you!

Love from me !