refactor: migrate library to TypeScript

[Josh-Cena]

So here it is—a library completely in TypeScript! This will be the first step towards v2.

What I did:

• Made src/ the TS root and dist/ the output;
• Implemented ReadingTimeStream as a class;
• Configured ESLint to be TS-compatible.

How is publishing different?

The dist and src folders should both be published, and since the former is now gitignore-d, it won't be available until you run npm run build. I've configured the prepublishOnly script to run build every time when running npm publish.

Expected output:

npm notice 2.1kB README.md            
npm notice 142B  lib/index.d.ts       
npm notice 258B  lib/index.js         
npm notice 262B  lib/reading-time.d.ts
npm notice 3.3kB lib/reading-time.js  
npm notice 553B  lib/stream.d.ts      
npm notice 2.1kB lib/stream.js        
npm notice 1.1kB license              
npm notice 957B  package.json         
npm notice 139B  src/index.ts         
npm notice 3.1kB src/reading-time.ts  
npm notice 1.0kB src/stream.ts        
npm notice 694B  src/types.d.ts       
npm notice 122B  tsconfig.json

Note: after merging, please publish it as 2.0.0-alpha.0, because we're only halfway through the v2 milestone, but I'd still like to have a published version to test the current changes in other projects.

Breaking Changes

• The IOptions and IReadTimeResults no longer exist, in favor of the Options and ReadTimeResults types;
  • Why? The TypeScript team explicitly discourages prefixing interfaces with I.
• The ReadingTimeStream is no longer instantiable without explicitly using new;

  const {ReadingTimeStream} = require('reading-time');
  
  // Instead of:
  fs.createReadStream('foo')
    .pipe(ReadingTimeStream)
  
  // Please use:
  const analyzer = new ReadingTimeStream()
  fs.createReadStream('foo')
    .pipe(analyzer)

  • Why? This makes it clearer that ReadingTimeStream is a class rather than a function. In year 2021, we should embrace strict type enforcement and stay away from the wackiness of weak typing.

[ngryman]

Thanks again for the great work 🙌

This LGTM for the first step towards v2. One question on the top of my mind: do you expect to convert tests to Typescript as well in a follow-up PR?

Also at this point, I think it would make sense to add you as a collaborator to this project. I'm going to do that right now 🚀

[ngryman]

I think this should work:

Suggested change

	import readingTime from './reading-time'
	import ReadingTimeStream from './stream'
	// Wacky way to support const readingTime = require('reading-time') :(
	// Basically we can't use ES import/export anymore because re-assigning module.exports
	// decouples it from the exports object, which TS export compiles to
	module.exports = readingTime
	module.exports.default = readingTime
	module.exports.ReadingTimeStream = ReadingTimeStream
	import readingTimeFn from "./reading-time";
	export default readingTimeFn;
	export const readingTime = readingTimeFn;
	export { default as ReadingTimeStream } from "./stream";

[Josh-Cena]

The problem with export default readingTimeFn; is it's transpiled to module.exports.default = readingTimeFn. I need to support the require() without .default because that seems less straightforward.

I've asked the TS community if they have anything good and let's wait for a couple of days to see 👀

[Josh-Cena]

do you expect to convert tests to Typescript as well in a follow-up PR?

Yes, I do😁 Not so experienced with Mocha so I'll do it when I'm migrating to Jest

Thanks for inviting! Feel honored

[Josh-Cena]

@ngryman So let's merge this for now, and you can make another 2.0.0-alpha.0 release so I can test in my repo 😏 We can figure out about the right export method later