esmjs / esmc - Draft

ESMC is Smart Modules Compiler. The Power of Intelligence. ESM are Sweet Modules. The Power of Intelligence. ESMJS, Sweet Modules JavaScript. The Power of Intelligence.

• Full power of ES Modules - using esm loader, creating ESM <-> CJS bridge
• Full power of Babel - TypeScript, React, Nodejs 8/10, Browsers, Preset Env, Stage 3
  • transpiles to Node 8/10 in dist/nodejs with .mjs files
  • transpiles to Browserlist's >=1%, not ie query in dist/browsers with .js files
  • generates dist/typings files, ready for the types field in package.json
  • both outpus for nodejs and browsers are using ES Modules, intentionally
    • 1. because Webpack/Rollup need es modules
    • 2. because we generates the dist/nodejs/index.js which is esm bridge
  • the browsers output only needs to be bundled, no transpilation needed
• Full power of ESLint - AirBnB, Prettier, React, Nodejs, TypeScript
• Full power of TypeScript - tslint, type checking and type distribution
• Full power of bundling - Rollup/Webpack (rollup by default)
• Intelligent workflow and target detection
  • easy start with esm init
  • you are ready to esm watch, esm build and esm bundle
• If you don't want type things, just write JS/JSX in .mjs source files
• If you want static typing and etc, write .ts and .tsx source files

How it works

Scenario 1: You want TypeScript

If you love and want static typing, just write .ts or .tsx files. Here should be noted that TypeScript forces us to use different extension if we want to write some JSX (the .tsx extension).

We don't use the TypeScript compiler tsc binary. We transform the source files in src/ directory with Babel 7 using the @babel/preset-typescript. This gives us the full power of Babel such as Preset Env, Stage 3 and React. And the Stage 3 preset isn't scary - we just use it because the Class Properties proposal (in the case when we not transpiling typescript), Dynamic Import and import.meta syntax plugins. The @babel/preset-env is used just because we want to have ability to transpile for specific browsers/nodejs versions. Here for browsers we use the >=1%, not ie query of Browserlist.

So, what's the execution order?

1. Run tsc without emitting type declaration files, just type checking.
2. Run eslint --fix over the source files, which does the fixing and formatting with Prettier.
3. Run tsc only emitting declaration files, which creates dist/typings directory.
4. Compile the .ts/.tsx files into .js files to dist/nodejs and dist/browsers folders.
5. Run prettier 'dist/**/*' --write to only prettify the output of Babel.
6. Rename all .js files from dist/nodejs folder to have .mjs extension.
7. Generate a dist/nodejs/index.js file which in turn uses the esm package to load the .mjs files.

Scenario 2: You love modern JavaScript.

In case you don't love static typing and TypeScript/FlowType, you can just write awesome modern JavaScript/JSX into .mjs files in your src/ directory and we will disable the typescript preset. It will allow you to use everything that Node 8/10 supports plus the Class Properties & Dynamic Import. The rest is the same - we compiles these files to dist/nodejs and dist/browsers folders, using the same Browserlist query for the browsers.

So, what's the execution order?

1. Run eslint --fix over the source files, which does the fixing and formatting with Prettier.
2. Compile the .mjs files into .mjs files at dist/nodejs (with Babel's --keep-file-extension)
3. Compile the .mjs files into .js files at dist/browsers
4. Run prettier 'dist/**/*' --write to only prettify the output of Babel.
5. Generate a dist/nodejs/index.js file which in turn uses the esm package to load the .mjs files.

Bundling: Rollup / Webpack

And so, the only thing that left to be done is bundling, but that's optional only if you need to have browser bundles. You can use either Rollup or Webpack to bundle the dist/browsers/index.js entry. Notice that you don't need to transpile, but only need to resolve all deps and make single bundle file which will be used in the browsers (or multiple bundle chunks, using Code Splitting).

Code Style, Linting: ESLint / AirBnB / Prettier

We use very well fine-tuned ESLint config which integrates AirBnB preset (including their React and JSX configs) and the Prettier plugin. There are things that are handled by TypeScript/TSLint defaults, so they are disabled from the ESLint. There are other things that are disabled from AirBnB, so they won't conflict with the Prettier or TypeScript. But we intentionally don't use the eslint-config-prettier, instead we disabled one by one rules that are not okey with the Prettier formatting.

We also use the typescript, import, node, promise ESLint plugins with few eslint-import resolvers, such as the eslint-import-resolver-typescript and eslint-import-resolver-node.