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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

Project - Calculator

Project — Calculator

Mission: Backstage Toolkit

The awards desk needs one calculator that delegates each operation to a small helper. Build it in script.js and check its results in the Console.

Put your function declarations and conditionals knowledge together to build a simple calculator engine. Function expressions are introduced in the next lesson; they are not required here.

Worked example

One function can hand work to another. This separate postage example returns a value without changing the page:

javascript
function basePostage(weight) {
  return weight * 2;
}

function postage(weight, express) {
  if (express) return basePostage(weight) + 5;
  return basePostage(weight);
}

console.log(postage(3, true)); // 11

Your Task

  1. Implement add(a,b).
  2. Implement subtract(a,b).
  3. Implement multiply(a,b).
  4. Implement divide(a,b), returning null on zero divisor.
  5. Implement calculate(a,op,b) for +, -, *, / (calling helpers), returning null for unknown operator.
  6. Log 10 + 5 = 15 using calculate(10,"+",5).
  7. Log 8 / 0 = Error: Division by zero using calculate(8,"/",0).
Hint 1
1 / 3
HINT 1

Each operation is a separate function: add, subtract, multiply, divide.

HINT 2

The calculate(a, op, b) function calls the right operation using an if/else or switch.

HINT 3

Guard against division by zero: return null (or a special message) when b is 0.

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