Choosing the structure

JavaScript · Unit 8: More on arrays

An array is a line: order matters, repeats are fine and you read by position.

An object describes a single thing with properties you know ahead of time: the name, the age, the price.

const line = ["Ava", "Leo", "Ava"];
const film = { title: "Coco" };
console.log(line[2], film.title);

Prints

Ava Coco

The rest of the explanation is in the lesson, which is part of the full plan.

Exercises in this lesson

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

1. Multiple choice
You store the songs for the party in the order they'll play, and a song can play twice. What do you use?
2. Multiple choice
You store the details of a phone, its brand, its price and its memory. What do you use?
3. Complete the code
Complete it with the structure that describes a film.
4. Multiple choice
In a sign-up, each email can be registered only once, and you need to know quickly if one is already there. Which structure does that on its own?
5. Predict the output
What does this code print?
6. Find the bug
This program should print how many different people voted, "Voters: 2". Which line has the error?
7. Put the lines in order
Order the function that returns the first name that lines up twice, or "Nobody" if no one repeats.
8. Multiple choice
What's a real reason to prefer a Map over an object?
9. Find the case that fails
countDistinct(vals) should return how many different values there are. The number 1 and the string "1" count as different. Which call does it fail with?
10. Predict the output
You put several structures together. What does it print?

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