An object is a collection of properties. Each property has a key (or name) and a value. Objects allow you to group related data together.

The object has properties with keys name, age, and city.

Each key is connected to a value (for instance, name is connected to "Alice").

You can read the value of a property using dot notation or bracket notation. For example:

You can update a property by using dot notation (or bracket notation) on the object. For example:

To add a new property, simply assign a value to a new key.

Assign it an object with the keys: name (value: "Alice"), age (value: 25), and city (value: "Wonderland").

Print the entire object using console.log(person).

index.js

index.test.js

Creating and Printing an Object

Assign it an object with the properties: make (value: "Toyota"), model (value: "Camry"), and year (value: 2010).

Print the updated year using console.log(car.year).

Accessing and Updating Object Properties

Assign it an object with the properties: title (value: "1984") and author (value: "George Orwell").

Add a new property pages with the value 328.

Then remove the property author from the object.

Print the final object using console.log(book).

Adding and Removing Object Properties

## What Is an Object?

An object is a collection of properties. Each property has a key (or name) and a value. Objects allow you to group related data together.

For example:

```javascript
let person = {
  name: "Alice",
  age: 25,
  city: "Wonderland"
};
```

In this example:

- The variable person holds an object.
- The object has properties with keys name, age, and city.
- Each key is connected to a value (for instance, name is connected to "Alice").

---

## Accessing Object Properties

You can read the value of a property using dot notation or bracket notation. For example:

```javascript
console.log(person.name);     // prints "Alice"
console.log(person["age"]);   // prints 25
```

---

## Updating Object Properties

You can update a property by using dot notation (or bracket notation) on the object. For example:

```javascript
person.city = "New Wonderland";
console.log(person.city);  // prints "New Wonderland"
```

---

## Adding and Removing Object Properties

### Adding

To add a new property, simply assign a value to a new key.

```javascript
person.occupation = "Adventurer";
console.log(person.occupation);  // prints "Adventurer"
```

### Removing

To remove a property, use the **delete** operator.

```javascript
delete person.age;
console.log(person.age);  // prints undefined
```

---

## Exercises

@exercise a78447650c80

@exercise 826c1e9717a8

@exercise 20a9d84ef59d


- Luo muuttuja nimeltä henkilo käyttäen **let**-avainsanaa.
- Määritä sille objekti, jonka avaimet ovat: nimi (arvo: "Sherlock Holmes"), ika (arvo: 26) ja kaupunki (arvo: "Lontoo").
- Tulosta koko objekti käyttäen console.log(henkilo).

Objektin luominen ja tulostaminen

- Luo muuttuja nimeltään auto käyttäen **let**-avainsanaa.
- Määritä sille objekti ominaisuuksilla: valmistaja (arvo: "Toyota"), malli (arvo: "Camry") ja vuosi (arvo: 2010).
- Päivitä vuoden ominaisuus arvoon 2020.
- Tulosta päivitetty vuosi käyttäen console.log(auto.vuosi).

Objektien ominaisuuksien päivittäminen

- Luo muuttuja nimeltä kirja käyttäen **let**-avainsanaa.
- Määritä sille objekti ominaisuuksilla: otsikko (arvo: "1984") ja kirjailija (arvo: "George Orwell").
- Lisää uusi ominaisuus sivut arvolla 328.
- Poista sitten kirjailija objektista.
- Tulosta lopullinen objekti käyttäen console.log(kirja).

Objektien ominaisuuksien lisääminen ja poistaminen

Objects: Grouping Data with Key–Value Pairs

Learn programming with JavaScript, arguably the most important and versatile programming language in today's world, at least for web development.

Welcome to Hakatemia’s beginner-friendly JavaScript course, where you will learn the fundamentals of programming with JavaScript. In today’s world, JavaScript is one of the most popular and versatile programming languages—especially in web development, where it holds a unique position: no other programming language can run both in the browser and on the server. For this reason, JavaScript has become extremely popular and is used for developing user interfaces (React, Vue, Angular, Svelte, etc.), back-end systems (NodeJS/Express, HAPI, etc.), and full-stack solutions (NextJS, NuxtJS, etc.).

These JavaScript frameworks will be covered in later Hakatemia courses, but before we get there, we must first master the basics of JavaScript programming. This course is designed precisely for that purpose.

Throughout the course, you’ll learn core programming concepts such as variables, operators, conditional statements, functions, arrays, and objects. Each module is divided into small, manageable segments with plenty of practical exercises.

This course is being released as a beta—the first part of Hakatemia’s comprehensive web development curriculum—and it is the first course that uses Hakatemia’s new programming exercise environment. Please provide feedback using the button at the bottom of the page or on Discord if you encounter any issues!

Objects: Grouping Data with Key–Value Pairs

What Is an Object?

Learn to hack — start here