Object:

• Object has key-value pairs.

• In JavaScript objects, the keys are always stored and treated as strings, regardless of how they are specified. This means that even if you define a key as a number or a symbol, it will be converted to a string internally.

• The data-type of value could be of any type like string, number, object, function, array or boolean.

Various Methods To Declare An Object

1. Object Literal Notation :

    const person = {
        firstName: 'Vivek',
        lastName: 'Bindra'
    };
   
    console.log(person);
    // Output: {firstName: 'Vivek', lastName: 'Bindra'}
   

2. new Object() syntax :

    const car = new Object();
    car.make = 'Toyota';
    car.model = 'Camry';
    car.year = 2022;
   
    console.log(car);
    // Output: {make: 'Toyota', model: 'Camry', year: 2022}
   

3. Object.create() method :

    const animal = Object.create(null);
    animal.type = 'Dog';
    animal.sound = 'Bark';
   

4. Using constructor function :

    function Person(firstName, lastName, age){
        this.firstName = firstName;
        this.lastName = lastName;
        this.age = age;
    }
    const person1 = new Person('Radhika', 'Pawar', 27)
   

---

How To Access Object Values

1. Dot notation :

    const user = {
        firstName: "Harshal",
        lastName: "Dongare"
    } 
    console.log(user.firstName);     // Output: "Harshal"
   

2. Bracket Notation :

    const user = {
        firstName: "Harshal",
        lastName: "Dongare"
        "full name": "Harshal Dongare"
    } 
    console.log(user["lastName"]);     // Output: "Dongare"
    console.log(user["full name"]);     // Output: "Harshal Dongare"
   

---

How To use Key as a Symbol In Object

const mySym = Symbol("key1");

const obj1 = {
    firstName: "Harshal",
    lastName: "Dongare",
    [mySym] : "myKey1"
}
console.log(typeof obj1[mysym]); // Output: "myKey1"

---

Method To Apply On Object

1. Object.freeze(objName) :

   A method that is used to freeze an object. When an object is frozen, it's properties cannot be added, removed, or modified.

    // Creating a sample object
    const person = {
      name: 'John',
      age: 30
    };
   
    // Freeze the object
    Object.freeze(person);
   
    // Try to modify the object
    person.age = 40; // This change will not take effect
   
    // Try to add a new property
    person.gender = 'Male'; // This addition will not take effect
   
    // Try to delete a property
    delete person.name; // This deletion will not take effect
   
    // The object remains unchanged
    console.log(person); // Output: { name: 'John', age: 30 }
   

2. Object.keys(objName) :

   It is a built-in javascript method that returns an array of all keys present inside an object.

    const person = {
      firstName: 'John',
      lastName: 'Doe',
      age: 30,
    };
   
    const keys = Object.keys(person);
    console.log(keys); // Output: ['firstName', 'lastName', 'age']
   

3. Object.values(objName) :

   A method that returns an array of all given values of keys present inside an object.

    const person = {
      firstName: 'John',
      lastName: 'Doe',
      age: 30,
    };
   
    const values = Object.values(person);
    console.log(values); // Output: ['John', 'Doe', 30]
   

4. Object.entries() :

   A method returns an array of a given object's key-value pairs, in the form of [key, value] arrays.

    const person = {
      firstName: 'John',
      lastName: 'Doe',
      age: 30,
    };
   
    const entries = Object.entries(person);
    console.log(entries);
    // Output:
    // [
    //   ['firstName', 'John'],
    //   ['lastName', 'Doe'],
    //   ['age', 30]
    // ]
   

5. hasOwnProperty(propertyName) :

   A method to check whether the given property name present inside an object or not. It returns boolean value based upon the results.

    const person = {
      firstName: 'John',
      lastName: 'Doe',
      age: 30,
    };
   
    console.log(person.hasOwnProperty('firstName')); // Output: true
    console.log(person.hasOwnProperty('middleName')); // Output: false
   

---

How To Merge Two Objects

1. Object.assign() method :

   This method copies all enumerable own properties from one or more source objects to a target object and returns the target object.

    const target = { a: 1, b: 2 };
    const source = { b: 3, c: 4 };
    const merged = Object.assign({}, target, source);
    console.log(merged); // Output: { a: 1, b: 3, c: 4 }
   

2. spread syntax :

   The spread syntax allows for easy merging of objects by spreading the properties of one or more objects into a new object.

    const target = { a: 1, b: 2 };
    const source = { b: 3, c: 4 };
    const merged = { ...target, ...source };
    console.log(merged); // Output: { a: 1, b: 3, c: 4 }
   

---

Destructuring Of An Array

Object destructuring is a feature in JavaScript that allows you to extract multiple properties from an object and assign them to variables in a more concise and readable way.

Syntax:

const { property1, property2 } = object;

1. Basic Object destructuring

    const person = {
      firstName: 'John',
      lastName: 'Doe',
      age: 30,
    };
   
    const { firstName, lastName } = person;
   
    console.log(firstName); // Output: 'John'
    console.log(lastName); // Output: 'Doe'
   

2. Renaming Variables

    const person = {
      firstName: 'John',
      lastName: 'Doe',
      age: 30,
    };
   
    const { firstName: fName, lastName: lName } = person;
   
    console.log(fName); // Output: 'John'
    console.log(lName); // Output: 'Doe'
   

3. Nested Destructuring

    const person = {
      name: {
        first: 'John',
        last: 'Doe',
      },
      age: 30,
    };
   
    const { name: { first, last } } = person;
   
    console.log(first); // Output: 'John'
    console.log(last); // Output: 'Doe'
   

---