A version of the Gilded Rose kata in JavaScript with approval testing.

See also

About the Gilded Rose kata:

• https://iamnotmyself.com/2011/02/14/refactor-this-the-gilded-rose-kata/
• https://github.com/NotMyself/GildedRose
• https://github.com/emilybache/GildedRose-Refactoring-Kata

About approval tests:

• https://approvaltests.com/

Videos demonstrating or about the kata:

• https://www.youtube.com/watch?v=q11gydDAMSo
• https://www.youtube.com/watch?v=1bJzZvGLVzc

About type checking JavaScript files:

• https://github.com/microsoft/TypeScript/wiki/Type-Checking-JavaScript-Files
• https://github.com/microsoft/TypeScript/wiki/Architectural-Overview
• https://www.typescriptlang.org/docs/handbook/jsdoc-supported-types.html

Type checking learnings

• Only files marked by @ts-check are checked (can be configured, a black list is also possible)
• Type errors are displayed on the fly in IDEs (tested on Vim + ALE)
• Type checking can be run in watch mode
• Type checking can be run in the CI environment
• No runtime cost: type annotations are in comments
• No additional build phase, no additional deployment phase
• Function arity of @param annotated functions is checked
• There is a type inference mecanism, no need to annotate everything
• @private and @readonly annotation for class fields
• Union Types
• Parametric Types
• Allows "rename method" and "rename field" automated refactorings, maybe more ?
• Types used only in comment annotations can (should?) be declared only in comment annotations
• We can declare and implement typechecked interfaces (@interface and @implements)