Summary - Objects

Combine objects, methods and spread to write a phone book.

Summary - Objects

In this group you looked at objects from four angles: the literal syntax, property access (dot and bracket), computed properties for dynamic names, and methods for behaviour. The spread operator gave a short way to copy and merge.

You can combine these to build real data structures. A phone book, for example: contact objects gathered in a root object, methods to add contacts, and spread to update them.

In the final task you will write a small phone book. You will add a method to insert contacts and another to look them up by name. You will also use object spread and bracket access.

Exercise Phone book object

Define an object named contacts. Its add(name, phone) method should insert a new contact via this[name] = phone. Add Ayşe with phone 5551, then print contacts['Ayşe'] with console.log.

Show example solution

const contacts = { add(name, phone) { this[name] = phone; } };
contacts.add('Ayşe', '5551');
console.log(contacts['Ayşe']);

Exercise Look up in the phone book

Define the contacts object as { Ayşe: '5551', Alex: '5552' }. Its lookup(name) method returns this[name]. Print the result of contacts.lookup('Alex') with console.log.

Show example solution

const contacts = { Ayşe: '5551', Alex: '5552', lookup(name) { return this[name]; } };
console.log(contacts.lookup('Alex'));

Test yourself

Match the concepts

{ }

Object literal
.name

Dot access
[key]

Computed/dynamic access
...obj

Spread copy
greet() { }

Method definition
How do you look up in a phone book?
- Add a method
- Walk with forEach
- Copy with spread
- Bracket access by name
Show answer

Bracket access by name — since the book is an object, bracket access by name is the fastest lookup.

Update with spread

const base = { a: 1, b: 2 };
const copy = { ____, c: 3 };

Show answer

const base = { a: 1, b: 2 };
const copy = { ...base, c: 3 };

Next lesson: Defining functions

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