Objects: Grouping Data with Key–Value Pairs

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:

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:

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:

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.

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

Removing

To remove a property, use the delete operator.

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

Exercises