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← Introduction to JavaScript
○What is JavaScript?○Your First JavaScript Code○Data Types○Type Checking○Inspect Values in the Console○Inspect the Queue Report○Trace a Faulty Calculation○Repair the Score Calculation✦Module Quiz
○Declaring Variables○let and const in Practice○Operators○Type Conversion○Group and Convert Expense Inputs○Calculate the Event Expense Total○Track a Changing Points Tally○Adjust a Ticket Price✦Module Quiz
○Conditionals○Demo: Combined Conditions Before FizzBuzz○Challenge: FizzBuzz Announcer○Switch Statement○Demo: Switch a Venue Sign○Challenge: Power Loadout○For Loops○While Loop○Break and Continue○Demo: Stop a Ticket Scan○Challenge: Number Guess Referee○Demo: Rainfall Routing Walkthrough○Exercise: Score Batch Report✦Module Quiz
○Defining Functions○Arrow Functions○Scope○Closures○Project - Calculator○Function Expressions○Demo: Ticket Pricing Walkthrough○Exercise: Shipping Labels with Defaults○Demo: Seat Ledger Closure Walkthrough○Exercise: Private Budget Ledger✦Module Quiz
○Arrays○Demo: Student Scoreboard○Challenge: Student Course Scoreboard○Array Mutation Methods○Array Slice and Concat○Array Iteration Methods○Multidimensional Arrays○Destructuring○Array Reverse and Sort○Array Fill○Array Find and Includes○Array Flat and FlatMap○Array Reduce, Some, and Every○Demo: Charging Rack Restock Report○Exercise: Pantry Restock Plan✦Module Quiz
○Object Key-Value Pairs○Student Course Record○Object Methods and Destructuring○Map and Set Collections○Playlist Lookup○Number and BigInt Boundaries○Ticket Ledger○JSON○Math and Date○Date Basics○Demo: Supply Bin Audit○Exercise: Volunteer Shift Audit○Demo: Workshop Attendance Feed○Exercise: Parcel Scan Feed✦Module Quiz
○String Methods○Template Literals○Regular Expressions○Demo: Build a Reminder with Template Literals○Exercise: Format Pantry Pickup Messages○Demo: Validate a Time Slot with Regex○Exercise: Validate Storage Shelf Labels✦Module Quiz
○Higher-Order Functions○Callbacks○map, filter, and reduce○Demo: Student Register with map○Challenge: Student Register○Recursion○Project - Data Transform Pipeline○Demo: Handle an Error-First Callback○Exercise: Report Seat Reservation Results○Demo: Summarize Completed Bike Rides●Exercise: Summarize Delivered Parcels✦Module Quiz
○Demo: A notebook object○OOP Introduction○Demo: Independent workshop passes○Classes○Demo: An inherited notice○Inheritance○Demo: A private seat counter○Encapsulation○Demo: Equipment desk checkout○Project: Library Checkout✦Module Quiz
○Demo: Callback Timing○Exercise: Asynchronous JavaScript○Demo: Promise Rehearsal○Exercise: Promises and Async Await○Demo: Offline API Coordination○Exercise: Async API Simulation○Demo: Partial Results Bulletin○Project: Resilient Awards Feed○Demo: Retry a Local Delivery○Project: Reliable Score Delivery✦Module Quiz

Exercise: Summarize Delivered Parcels

Prepare a delivery summary

The bike-ride demo produced a single total. A parcel desk needs a reusable report of count and kilograms delivered, ignoring parcels that are still in transit.

summaryFor(deliveries) must return { count, totalKg } without changing the input array. Use filter, map, and reduce to compose the calculation. formatSummary(summary) turns that result into one Console-friendly sentence.

Worked example

This unrelated activity report composes the same filter → map → reduce pattern:

javascript
const readings = [{ active: true, minutes: 20 }, { active: false, minutes: 40 }];
const minutes = readings.filter(item => item.active)
  .map(item => item.minutes)
  .reduce((total, value) => total + value, 0);
console.log(minutes); // 20

Your Task

  1. Complete summaryFor(deliveries) with filter, map, and reduce (initial sum 0) to count delivered parcels and total their kilograms; empty input yields { count: 0, totalKg: 0 }.
  2. Complete formatSummary(summary) to return a sentence using the supplied count and totalKg fields.
  3. Log formatSummary(summaryFor(deliveries)) on its own line.

Functional programming complete

You can now compose callbacks and array transformations into reports. Take the section quiz to review the patterns.

Hint 1
1 / 2
HINT 1

Filter for delivered records; map each weightGrams to kilograms by dividing by 1000.

HINT 2

Reduce from 0 so there is a numeric total even when nothing was delivered.

Take the Quiz →
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