Planning Discussion for a move to TypeScript

[duluca]

This is a planning discussion thread. Comments may be used to share code snippets and ideas or to add/correct pros/cons list.

Plan

• Propose Interfaces that can be implemented in an unintrusive way so Type Definitions can be auto generated.
• Identify and document challenging areas of the code base, along with a TypeScript code snippet that overcomes the challenge (i.e. function overloading https://www.typescriptlang.org/docs/handbook/functions.html, default parameters, Interface inheritance, constructor, nested generics)

Pros

• Reduces amount of dev tools required, i.e. babel wouldn't be needed as transpiler anymore
• Helps dom support with TypeScript's robust transpiling support for ES8 to ES3.
• More maintainable code base using generics and type information
• JavaScript developers consuming testdouble in js can benefit from type definitions, inline documentation and auto-complete
• TypeScript developers consuming testdouble in ts can benefit from rich generics support
• Type definitions would be automatically generated and wouldn't have to be manually maintained

Cons

• A rewrite is a rewrite is a rewrite: a phased approached could be developed to ease the transition (i.e. Typed Interfaces to proxy existing JavaScript implementations)
• Risky, testdouble depends on JavaScript quirks and single threaded execution to guess what the developer means by pulling the last item on the stack. A plugin may be required to provide such features to developers. While this would greatly reduce complexity of the codebase and open it up for even richer features. However, this in turn increases development and continued maintenance effort.

[duluca]

@searls Here's a good intro to creating TypeScript-based npm packages: https://dev.to/dkundel/writing-a-nodejs-module-in-typescript

Here's a TypeScript library starter that encapsulates best practices for creating packages that can target node and the browser which is what's needed for this project: https://github.com/Hotell/typescript-lib-starter

I'm going to update my TypeScript library https://github.com/duluca/documentts/ to test out the config and report back the findings.

[searls]

Closing this issue since technically we have migrated to typescript, even though 99% of the code files are still .js