Objects

Object notation

In JavaScript, we can create a new object using braces like this: {}. Let's see how this works with an example.

Say we're writing software to manage a library, so we might want to represent a book as an object:

const book = {
  title: "The Handmaid's Tale",
  author: 'Margaret Atwood',
  year: 1985,
  isbn: '9780099740919',
  isAvailable: true
}

We can see that a JavaScript object is made up of properties - pairs of keys and values.

The value of an object property can be pretty much anything. In our example book, we've got a string, a number, and a boolean.

Accessing properties

Now that we've structured the book data, we can access its properties using the dot . notation:

js

const book = {
  title: "The Handmaid's Tale",
  author: 'Margaret Atwood',
  year: 1985,
  isbn: '9780099740919',
  isAvailable: true
}

console.log(`${book.title} by ${book.author}`)

output

The Handmaid's Tale by Margaret Atwood

Updating properties

Say we want to update the availability of the book.

We can do this in a similar way to assigning a variable:

js

const book = {
  title: "The Handmaid's Tale",
  author: 'Margaret Atwood',
  year: 1985,
  isbn: '9780099740919',
  isAvailable: true
}

// Change the value of the .isAvailable property
book.isAvailable = false

console.log(book)

output

{
  title: "The Handmaid's Tale",
  author: 'Margaret Atwood',
  year: 1985,
  isbn: '9780099740919',
  isAvailable: false
}

Adding properties

We can also use this to add a new property. Say we want to add a borrower property to the book object:

js

const book = {
  title: "The Handmaid's Tale",
  author: 'Margaret Atwood',
  year: 1985,
  isbn: '9780099740919',
  isAvailable: true
}

book.borrower = 'Andy'

console.log(book)

output

{
  title: "The Handmaid's Tale",
  author: 'Margaret Atwood',
  year: 1985,
  isbn: '9780099740919',
  isAvailable: true,
  borrower: 'Andy'
}

We've just added a new property borrower to the book object, and set its value to 'Andy'.