Add native Node.js ES Modules support

Author: abdonrd

.gitignore

@@ -1,4 +1,3 @@
-.DS_Store
-_*
-node_modules
-lib
+dist/
+lib/
+node_modules/

.npmignore

@@ -5,19 +5,32 @@
   "description": "An Implementation of ES Observables",
   "homepage": "https://github.com/zenparsing/zen-observable",
   "license": "MIT",
+  "main": "./dist/cjs/index.js",
+  "exports": {
+    "require": "./dist/cjs/index.js",
+    "import": "./dist/es/index.js"
+  },
+  "module": "./dist/es/index.js",
+  "type": "commonjs",
   "devDependencies": {
     "@babel/cli": "^7.6.0",
     "@babel/core": "^7.6.0",
     "@babel/preset-env": "^7.6.0",
     "@babel/register": "^7.6.0",
+    "@rollup/plugin-babel": "^5.0.0",
     "eslint": "^6.5.0",
-    "mocha": "^6.2.0"
+    "mocha": "^6.2.0",
+    "rollup": "^2.14.0"
   },
   "dependencies": {},
   "scripts": {
-    "test": "mocha --recursive --require ./scripts/mocha-require",
+    "build": "rollup --config",
     "lint": "eslint src/*",
-    "build": "git clean -dfX ./lib && node ./scripts/build",
-    "prepublishOnly": "npm run lint && npm test && npm run build"
-  }
+    "prepare": "npm run build",
+    "prepublishOnly": "npm run lint && npm test",
+    "test": "mocha --recursive --require ./scripts/mocha-require"
+  },
+  "files": [
+    "dist/"
+  ]
 }

esm.js

@@ -0,0 +1,28 @@
+import { babel } from '@rollup/plugin-babel';
+
+function emitModulePackageFile() {
+  return {
+    name: 'emit-module-package-file',
+    generateBundle() {
+      this.emitFile({
+        type: 'asset',
+        fileName: 'package.json',
+        source: '{"type":"module"}',
+      });
+    },
+  };
+}
+
+export default {
+  input: ['src/index.js', 'src/extras.js'],
+  output: [
+    { dir: 'dist/cjs/', format: 'cjs', exports: 'named' },
+    { dir: 'dist/es/', format: 'es', plugins: [emitModulePackageFile()] },
+  ],
+  plugins: [
+    babel({
+      babelHelpers: 'bundled',
+      plugins: require('./scripts/babel-plugins'),
+    }),
+  ],
+};

extras.js

@@ -8,7 +8,6 @@ module.exports = [
   '@babel/plugin-transform-duplicate-keys',
   '@babel/plugin-transform-for-of',
   '@babel/plugin-transform-literals',
-  '@babel/plugin-transform-modules-commonjs',
   '@babel/plugin-transform-parameters',
   '@babel/plugin-transform-shorthand-properties',
   '@babel/plugin-transform-spread',

index.js

@@ -1,3 +1,6 @@
 require('@babel/register')({
-  plugins: require('./babel-plugins'),
+  plugins: [
+    ...require('./babel-plugins'),
+    '@babel/plugin-transform-modules-commonjs',
+  ],
 });

package-lock.json

@@ -1,4 +1,4 @@
-import { Observable } from './Observable.js';
+import { Observable } from './index.js';
 
 // Emits all values from all inputs in parallel
 export function merge(...sources) {

package.json

@@ -1,4 +1,4 @@
-import { Observable } from '../src/Observable.js';
+import { Observable } from '../src/index.js';
 
 beforeEach(() => {
   global.Observable = Observable;