Calculator
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- Accepts amount owed and amount paid. +
- Converts non-base paid currencies before calculating change. +
- Shows total change, returned change, shortfalls, and denomination breakdowns. +
+ A configurable cash-register calculator built to demonstrate product behavior, + maintainable code organization, and reliable automated tests. +
++ The app calculates the change that should be returned for a cash transaction. It + supports manual transactions, flat-file uploads, configurable currencies, editable + denominations, local transaction history, and a twist rule that can return random + denominations when the owed amount matches the configured divisor. +
++ The code is intentionally separated so the application can grow without turning one + component into the entire system. React pages focus on rendering, shared UI lives in + reusable components, and business logic stays in pure TypeScript domain modules. +
++ The test suite covers both the pure rule engine and the user-facing React workflows. + This keeps the most important behavior protected while still making refactors safe. +
+npm run check
+ Runs TypeScript typechecking followed by the Vitest suite.
+ Enter the amount owed and the amount paid to calculate change.
++ Need a flat-file example?{' '} + + Download sample input + +
++ If the owed amount in cents is divisible by {trickNumber}, the system returns + random denominations. +
+US denominations load by default. Use a preset or save edits for new change calculations.
++ {settingsMessage} +
+ ) : null} +All transactions are saved in this browser using local storage.
+Control the number that activates the twist rule.
++ When the owed amount in cents is divisible by this number, change is returned using + random denominations. +
++ Choose the base currency for owed amounts, denominations, and change results. The + base currency equivalent is always 1. +
++ {activeDenominationCount} of {denominations.length} denomination + {denominations.length !== 1 ? 's' : ''} enabled for change calculations. +
++ {settingsMessage} +
+ ) : null} + + + +Clear local storage and restore currencies, denominations, settings, and history.
+