Courses
JavaScript Intermediate: Write Code That Doesn't Fall Apart When the Data Changes
Check Yourself: Work With Real Data
Five scenario questions on array methods, JSON and dates. If you miss more than one, reread the lesson that covers it.
Course content
Join this Course
Sign in to save your progress.
-
Set Up Projects That Don't Break Each Other
-
Node.js and npm: Running JavaScript Outside the Browser
-
package.json and Lock Files: Same Install Every Time
-
-
-
Organize Code Other People Can Read
-
JavaScript Modules: import, export and Splitting One Big File
-
JavaScript Classes: When an Object Literal Is No Longer Enough
-
Destructuring and Spread Without the Confusion
-
-
-
Work With Real Data
-
Array Methods: map, filter, reduce and When a Loop Is Clearer
-
Working With JSON: parse, stringify and What Breaks
-
Dates in JavaScript Without Losing a Day
-
-
-
Waiting for Things
-
Callbacks to Promises: Why the Code Runs Out of Order
-
async/await and fetch: Calling a Real API
-
-
-
Prove It Works Before Someone Else Finds Out
-
try/catch and Custom Errors
-
Your First Tests With Vitest
-
-
- Final Check: JavaScript Intermediate
1.
orders.map(o => { o.total * 2 }) gives an array of undefined. Why?
2.
Your daily revenue report crashes on a day with no orders: "Reduce of empty array with no initial value". Fix?
3.
response.json() throws "Unexpected token '<', "<!DOCTYPE "... is not valid JSON". What did you most likely get?
4.
After JSON.parse(JSON.stringify(order)), order.createdAt.getFullYear() throws. Why?
5.
A customer in New York picks October 15. Your code does new Date("2026-10-15").getDate() and gets 14. Best fix?
About
Five scenario questions on array methods, JSON and dates. If you miss more than one, reread the lesson that covers it.
- Duration
- 5 min
- Last update
- 09/01/2026
Was this helpful?
0
0
Comments (0)
Sign in to commentNo comments yet.