#7 Javascript Objects | Javascript Hindi Course For Beginners ( 2023 )

// Example of Objects
const student = {
name:"Rohan kumar",
roll:1,
class:"12"
}
// Object are key-value pairs.
// name -> key , value -> Rohan kumar
// roll -> key , value -> 1

// Inside object we can store any data we want. like boolean , string
// number , array ,objects

How to Create Objects

// Frist way 

const obj = {}

// Second way 

const obj = new Object();

How to access values in object

const addharCardData = {
firstName:"Anshu",
lastName:"Raj",
dob:"01-01-2000",
adharNo:479382749328749,
address:{ village:"xyz",district:"ranchi",state:"jharkhand",}
}

// two ways to access object values
// first way 
const firstName = addharCardData.firstName;
// second way 
const first_name = addharCardData["firstName"];

How to update and create value in object

const addharCardData = {
firstName:"Rohan",
lastName:"kumar",
dob:"01-01-2000",
adharNo:479382749328749,
address:{ village:"xyz",district:"ranchi",state:"jharkhand",}
}

// Lets create a new key-value pair
addharCardData.fatherName = "Shayam Lal";
// lets modify existing values
addharCardData.adharNo = 7394732984739284;

We can also use function inside object

const addharCardData = {
firstName:"Rohan",
lastName:"kumar",
dob:"01-01-2000",
adharNo:479382749328749,
address:{ village:"xyz",district:"ranchi",state:"jharkhand",}
fullName:(){ return this.firstName + " " + this.lastName; }
}

// this -> this refers to current object 
// in this example -> this === addharCardData

const fullName = addharCardData.fullName();

Constructor function

// constructor function is another way of creating Object.
// Rule -> Constructor Function Starts with capital letter 

function Person (firstName,lastName,age) {
// this === Person 
this.firstName = firstName;
this.lastName = lastName;
this.age = age;
this.fullName = function() {
return this.firstName + " " + this.lastName;
}

}

// constructor function starts with new keyword 
const myFather = new Person("John", "Doe", 50);

How to duplicate object

// Object is reference data type 
// what is reference data type ?
/* Answer : Reference data type is a data type that holds a
reference to an object in memory, rather than holding its value directly */

// lets see with example 

const obj1 = {title:"obj1"} // allocate space in memory + address
const obj2 = obj1;
// when we assign obj1 to obj2 
// no new space created in memory
// only obj2 holds address of obj1

obj2.title = "obj2";
// when we try to change title of obj2 
// title of obj1 

console.log(obj1.title); // output : obj2

// how to avoide reference 
// and  create deep clone
// we can use spread operator

const obj1 = {title:"obj1"} 
const obj2 = {...obj1}; 

How to loop over Objects

const student = {
name:"Rohan kumar",
roll:1,
class:"12"
}
// this will give key of object
for( let key in student ){
console.log(key)
}

// for getting key and value same time 
for(let key of Object.entries(student)){
console.log(`${key}: ${value}`);
}

// Object.fromEntries
// Covert Map data type to object 

const entries = new Map([
  ['foo', 'bar'],
  ['baz', 42]
]);

const obj = Object.fromEntries(entries);

console.log(obj);
// Expected output: Object { foo: "bar", baz: 42 }

// Covert Object data type to Map 
// Object.entries
Object.entries(student)
console.log(obj);
// Expected output: [ [ 'name', 'Rohan kumar' ], [ 'roll', 1 ], [ 'class', '12' ] ]

// Object.keys
// convert object key into array
const object1 = {
  a: 'somestring',
  b: 42,
  c: false
};

console.log(Object.keys(object1));
// Expected output: Array ["a", "b", "c"]

// Object.values
// convert object value into array
const object1 = {
  a: 'somestring',
  b: 42,
  c: false
};

console.log(Object.values(object1));
// Expected output: Array ["somestring", 42, false]

// hasOwnProperty()
// check key exist or not

object1.property1 = 42;

console.log(object1.hasOwnProperty('property1'));
// Expected output: true

console.log(object1.hasOwnProperty('toString'));
// Expected output: false

Questions

// Sample Data
getVoteCount({ upvotes: 13, downvotes: 0 }) ➞ 13

getVoteCount({ upvotes: 2, downvotes: 33 }) ➞ -31

getVoteCount({ upvotes: 132, downvotes: 132 }) ➞ 0

// Sample Data
fiftyThirtyTwenty(10000) ➞ { "Needs": 5000, "Wants": 3000, "Savings": 2000 }

fiftyThirtyTwenty(50000) ➞ { "Needs": 25000, "Wants": 15000, "Savings": 10000 }

fiftyThirtyTwenty(13450) ➞ { "Needs": 6725, "Wants": 4035, "Savings": 2690 }

1. name

2. population

3. continent

cityFacts({
  name: "Paris",
  population: "2,140,526",
  continent: "Europe"
}) ➞ "Paris has a population of 2,140,526 and is situated in Europe"

cityFacts({
  name: "Tokyo",
  population: "13,929,286",
  continent: "Asia"
}) ➞ "Tokyo has a population of 13,929,286 and is situated in Asia"