README.md

Capstone 01 - Dino Park Dashboard

The scenario

Park HQ needs a dashboard that pulls user and post data from the API, crunches it into statistics, and presents a summary. This exercise ties together everything from the course: fetch with Promise.all, map/filter/reduce for data transforms, object literals with this for the dashboard report, and clean module boundaries.

The code is organised into domain folders with barrel index.js files controlling the public surface of each module.

Project structure

starter/
  data/
    fetch-data.js       ← data fetching logic
    index.js            ← barrel: exports { fetchParkData }
  analytics/
    transforms.js       ← pure transform functions
    index.js            ← barrel: exports { postsPerUser, topPosters, averagePostLength }
  dashboard/
    dashboard.js        ← report assembly
    index.js            ← barrel: exports { buildDashboard }
  index.js              ← entry point
  index.test.js         ← tests (imports through barrels)

What you will build

starter/data/fetch-data.js - Data fetching

fetchParkData(fetchFn) - fetch /users and /posts from jsonplaceholder in parallel using Promise.all. Parse both responses and return { users, posts }.

starter/analytics/transforms.js - Pure transform functions

Function	Description
postsPerUser(users, posts)	Return a Map<userId, count> using reduce. Include all users (0 for those with no posts).
topPosters(users, posts, n)	Return the top n users by post count as [{ id, name, postCount }], sorted descending.
averagePostLength(posts)	Return the average body.length across all posts, rounded to the nearest integer.

starter/dashboard/dashboard.js - Report assembly

buildDashboard(users, posts) - return an object with:

Property	Type	Description
userCount	number	users.length
postCount	number	posts.length
topPosters	array	Result of topPosters(users, posts, 3)
averagePostLength	number	Result of averagePostLength(posts)
summary()	method	Returns "Dashboard: <userCount> users, <postCount> posts, avg length <averagePostLength>" using this

Note: dashboard.js imports its helpers from ../analytics/index.js - cross-module imports go through barrels.

Getting started

Implement data/fetch-data.js and analytics/transforms.js first, then wire them into dashboard/dashboard.js. Run:

node starter/index.js

Verify

cd starter && pnpm install && pnpm test

The tests use mock data and a mock fetch function - no network access needed. They check each transform individually, the dashboard shape, the summary() output, and that both API endpoints are called.

Hints

• postsPerUser: reduce posts into a Map, then loop over users to ensure every user has an entry (even 0).
• topPosters can reuse postsPerUser internally.
• summary() must use this - it reads this.userCount, this.postCount, and this.averagePostLength.
• Math.round(total / posts.length) handles the rounding for average length.

Reference solution

solution/ folder