Objects · Lesson 23 of 45

Object basics

Group information about one thing in one place.

8 minutes3 games

An object groups properties inside { }, each with a name (key) and a value. Read one with a dot, user.name, or brackets, user["name"], when the name is in a variable or has a space.

student
- name: "Youssef"
- level: 3
- skills
  - 0: "HTML"
  - 1: "JS"

Objects can hold arrays and other objects.

JavaScript

const student = {
  name: "Youssef",
  level: 3,
  skills: ["HTML", "JS"],
  "favorite color": "blue",
}

student.level = 4           // change
student.city = "Cairo"      // add
delete student.skills       // remove

const key = "name"
console.log(student[key], student.level, student["favorite color"])
console.log("city" in student)

Looping over an object

JavaScript

const prices = { tea: 10, coffee: 25, juice: 18 }

console.log(Object.keys(prices))
console.log(Object.values(prices))
for (const [drink, price] of Object.entries(prices)) {
  console.log(`${drink}: ${price} EGP`)
}

Quick question

How do you read the page count in const book = { pages: 300 }?

Spot the bug

One line prints undefined instead of the price. Which?

Exercise

Print the sum of every price in the object (53).

Expected output: 53

JavaScript

const prices = { tea: 10, coffee: 25, juice: 18 }

Learn more from

Played 0 of 3 games

JavaScript

Objects · Lesson 23 of 45

Object basics

Group information about one thing in one place.

8 minutes3 games

An object groups properties inside { }, each with a name (key) and a value. Read one with a dot, user.name, or brackets, user["name"], when the name is in a variable or has a space.

student
- name: "Youssef"
- level: 3
- skills
  - 0: "HTML"
  - 1: "JS"

Objects can hold arrays and other objects.

JavaScript

const student = {
  name: "Youssef",
  level: 3,
  skills: ["HTML", "JS"],
  "favorite color": "blue",
}

student.level = 4           // change
student.city = "Cairo"      // add
delete student.skills       // remove

const key = "name"
console.log(student[key], student.level, student["favorite color"])
console.log("city" in student)

Looping over an object

JavaScript

const prices = { tea: 10, coffee: 25, juice: 18 }

console.log(Object.keys(prices))
console.log(Object.values(prices))
for (const [drink, price] of Object.entries(prices)) {
  console.log(`${drink}: ${price} EGP`)
}

Quick question

How do you read the page count in const book = { pages: 300 }?

Spot the bug

One line prints undefined instead of the price. Which?

Exercise

Print the sum of every price in the object (53).

Expected output: 53

JavaScript

const prices = { tea: 10, coffee: 25, juice: 18 }

Learn more from

Played 0 of 3 games