Javascript Objects

#javascript #beginners #webdev #node

Object

Non-primitive data type.
Stores multiple collections of data.
Simply, js Object is a collection of key-value pairs.

key: value

Syntax

const object_name = { 
    key_1: value_1,
    key_2: value_2,
    key_n: value_n
}

Object Creation

const person = {
  firstName: 'Manikandan',
  lastName: 'MK',
  age: 24,
};

console.log(typeof person); // object
console.log(person); // { firstName: 'Manikandan', lastName: 'MK', age: 24 }

Explanation:
An object is a collection of key-value pairs.

   person                    - object name,
   firstName, lastName, age  - key/name. (left side)
   Manikandan, mk, 24        - value. (right side)

Key-value pairs are called properties.

ACCESSING OBJECT

1. Dot Notation

Syntax:

Object_name.key

Example:

const person = {
  firstName: 'Manikandan',
  lastName: 'MK',
  age: 24,
}; 

console.log(person.firstName); // Manikandan

2. Bracket Notation

Syntax:

  ObjectName["propertyName"]  (property name is nothing key name)

Example: 
const person = {
    firstName: 'Manikandan',
    lastName: 'MK',
    age: 24
    }

    console.log(person['firstName']);   // Manikandan

Nested Object

A nested Object is nothing but an Object containing another object.

Example:

const person = {
  firstName: 'Manikandan',
  lastName: 'MK',
  age: 24,
  physicalDetails: {
    height: 170,
    weight: 70,
  },
};

console.log(person.physicalDetails); // { height: 170, weight: 70 }
console.log(person.physicalDetails.height); // 170