Foundation project

Project: a learning progress report

Lesson 12 of 20 · 18 min · Module 4: Reliable features

Bring together functions, conditions, arrays, and objects to build the logic behind a learning dashboard.

Free. No installation: you write and run the code in your browser, and it is checked automatically.

By the end, you’ll be able to…

Break a feature into testable steps
Combine filter, map, and reduce
Return a stable result shape for edge cases

The idea

Each lesson has a title, minutes, and completed flag. Your report should describe completed work while leaving the original records intact.

const lessons = [
  {title: "Variables", minutes: 8, completed: true},
  {title: "Loops", minutes: 9, completed: false}
];

01Start with the contract

The output always has the same three fields. Decide what each means before choosing methods. Count and minutes are numbers; titles is an array of strings.

02Build and check one part at a time

Start with one completed lesson. Add an unfinished lesson and confirm the report does not change. Add another completed lesson, then try an empty list. These checks expose different mistakes.

Your project brief

Write reportProgress(lessons) to return {completed, minutes, titles}: the number of completed lessons, their combined minutes, and their titles in input order. Empty input returns {completed: 0, minutes: 0, titles: []}.

What the checks look for

Counts only completed lessons
Adds completed minutes and preserves title order
Handles an empty list
Does not mutate frozen records

Try it in the editor →

Take this with you

A complete feature handles typical data, empty data, and the promise it makes about the input.