Project: contact book

JavaScript · Unit 7: Objects

Your contact book is an array of objects: each contact has a name and a phone. Adding a contact means doing a push on the array.

const contacts = [];
contacts.push({
  name: "Leo",
  phone: "555-0202",
});
console.log(contacts.length);
console.log(contacts[0].phone);

Prints

1
555-0202

Exercises in this lesson

You do them in the app, which checks them on the spot and explains why.

1. Complete the code
Complete the function that builds a new contact to add to the book.
2. Predict the output
You look for Mia in the contact book. What does it print?
3. Write the code
Write lookup(contacts, name), which returns the phone of the contact with that name, or "Not found" if there isn't one.
4. Write the code
Write listAll(contacts), which returns an array of strings shaped like "Name: phone", in alphabetical order. For example, with Leo and Ava it gives ["Ava: 555-01", "Leo: 555-02"].

It opens in your browser. This lesson is part of the full plan; the first unit of each course is free.