Checkpoint: Working with Data

Five questions on this section. Answer all of them, then see your score and why each answer is right or wrong.

const names = expenses.map((e) => { e.label.toUpperCase(); }); gives an array of undefined. What is the fix?

Use forEach instead of map.
Remove the braces, (e) => e.label.toUpperCase(), or add return inside them.
Use filter instead of map.
Declare names with let instead of const.

What does [5, 25, 100].sort() return?

[5, 25, 100]
[5, 100, 25]
[25, 5, 100]
[100, 25, 5]

What does this log?

JavaScript

const settings = { currency: "USD", limits: { food: 400 } };
const copy = { ...settings };
copy.limits.food = 500;
copy.currency = "EUR";
console.log(settings.currency, settings.limits.food);

USD 400
EUR 500
USD 500
EUR 400

Which expression returns a saved discount of 0 as 0, and uses 10 only when no discount was saved?

user.discount ?? 10
user.discount || 10
user.discount ? user.discount : 10
user?.discount || 10

Pocket marks expenses as “reviewed” and checks isReviewed(id) for every item on every render. Which structure fits best for the reviewed ids?

A string of ids joined by commas.
A Map from id to the full expense object.
An array that you push each id into.
A Set of ids.

5 questions unanswered