React Retro online calculator

React calculator is an application developed using React-xstate-HTML5-CSS3-SASS frameworks which tries to implement a retro calculator functionalities and to host it online.

Demo

setup

Install dependencies - Type yarn install:fixed (this will install packages with the versions matching the committed yarn.lock versions)
Automated production build - Type yarn start to start development in your default browser.
First yarn install will also configure husky which has precommit hooks configure to run lint-staged which in turn will run the prettify, test and tsc compiler checks before committing the code

Implementation details

The react caclulator logic has been kept separately from the application code not to pollute the business logic with the application layers. I used x-state a javascript library that helps to implement finite state machines which suits the case as the calculator logic can be represented as a sequential steps/states and and the system will not be in two states at the same time. This also eliminates the need for a state management library like redux which might bring lack of transparency to the code as the developer have to navigate through different places (actions / reducers etc) to understand the flow. In this case, the stateMachine representation depicts which states the app has and transitions to different states and corresponding actions to run and with extra checks using guards. This also helps to write tests easier.

It can be represented as below:

stateDiagram-v2
    [*] --> Off
    Off --> Operand1: on AC button clicked

    Operand1 --> Off
    Operand1 --> Operator: on operands -> + - / * % √

    Operator --> Off
    Operator --> Operand2: on digits/decimal

    Operand2 --> Off
    Operand2 --> Result: on equal symbol/operands

    Result --> Operand1: on digits/decimal
    Result --> Operator: on operands
    Result --> Off

Folder structure

React-Calculator
│
│───README.md
│───tsconfig.json
│───package.json
│───eslint.json
│
│───application // contains application (react related code)
│   │───scss
│   │   └───theme. mixin, colors etc
│   │
│   │───components
│   │   │───Display
│   │   │───ButtonPanel
│   │   └───Button
│   │
│   └───RetroCalculator
│
└───domain // business logic
    │───calculator.state.machine.ts
    │───calculator.guards.ts
    │───calculator.dto.ts
    │───calculator.actions.ts
    └───calculator.constants.ts

TODO