Ultimate Refactoring TypeScript

Exercises

1. koans. Try to understand how JavaScript works with values and references through a series of koans.
2. valueAndReference. Uncomment the tests with correct result for koans in order that everything will work.
3. implementationChange. Make ShoppingCart that will work with a list of prices instead of only one price.
4. signatureChange. Try different levels:
   • At CsvBuilder, remove middle method
   • Use parallel change for use an object value ID instead of number at AuthenticationService.
   • Try to make it been smart: using parallel change + inline and finally a parameter object
   • Try to change the Player constructor for having only one.
5. implementationChange:
   • at ShoppingCart, try to use Price, instead of number
   • change all methods related to price as number in order to use Price
   • parallel implementation and manual replacement of callers
     • parallel implementation + inline method
     • wrap return object
6. moveResponsability:
   • God class
     • use extract delegate to move them to a new class
     • add parameter + make static + convert to instance
     • create class dependency + move + encapsulate field + inline
     • pull down
   • InvoiceService - feature envy:
     • make static + move + convert to instance
     • extract parameter + move
     • extract method + move
     • remove InvoiceService automatically
       • inheritance + create default constructor + inline constructor
7. dependencyChange:
   • Detect smell at package
   • Invert the dependency from Finder to UserRepository

Setup

Node v22 is required to run this project.

💡If you don't have it installed, we recommend the use of a version manager like nvm or fnm (a cross-platform alternative to nvm). After installing the manager, you can install the Node version by running: nvm use or fnm use.

Once you have Node installed, you can install the project dependencies by running:

npm install

Plugins

This project uses the following plugins:

• Vitest, a blazing fast test framework.
• Biome, a toolchain for linting and formatting.

ℹ️ If VSCode is your editor of choice, you can install the recommended extensions.

Run tests

You can run the tests by running:

npm run test

If you want to run the tests in watch mode, you can run:

npm run test:watch

Also, you can run the tests with coverage by running:

npm run test:coverage