Object

Object is a type of data in JavaScript that contains key-value pairs. These pairs are written within curly braces and separated by commas. For example:

const anObject = {
  key1: 'value1',
  key2: 'value2',
  string: 'Yay', // more string
  number: 1, // number
  boolean: true, // boolean
  anotherObject: {}, // another object
  aFunction: function () {}, // functions
  anArray: [] // array
}

Get the value of a property

Objects can store various types of values, including primitives and other objects. You can access object properties using dot notation. For example:

const macbook = {
  storage: '512gb'
}

const storage = macbook.storage // Dot notation
const storageAlt = macbook['storage'] // Bracket notation

Use dot notation for valid identifiers and bracket notation for invalid identifiers or when accessing properties through variables.

const objWithInvalidIdentifiers = {
  'First Name': "Reza"
}

const firstName = objWithInvalidIdentifiers['First Name'] // Bracket notation

Notes: Valid Identifiers

1. It must be one word
2. It must consist only of letters, numbers or underscores (0-9, a-z, A-Z,_)
3. It cannot begin with a number
4. It cannot be any of these reserved keywords

Anything that doesn’t follow these rules is an invalid identifier.

Set and Delete value of a property

You can also set or delete properties using both notations.

macbook.storage = '256gb' // Set property
delete macbook.storage // Delete property

Function are special objects

Function in JavaScript are special objects and can have properties. When functions are stored in objects, they are called methods.

const greeter = {
  sayHello: function (name) {
    console.log('Hello ' + name + '!')
  }
}

greeter.sayHello('Reza') // Hello Reza!

Summary

• Object store key-value pairs.
• Properties can be accessed using dot or bracket notation.
• Use dot notation for valid identifiers and bracket notation for invalid identifiers or variable-based access.
• Functions can be stored in objects as methods.