feat(esm): export pure ESM, no more CommonJS support

BREAKING CHANGE: Requires ESM and Node >= 12.20

Author: grantila

.github/workflows/branches.yml

@@ -18,7 +18,7 @@ jobs:
         node-version:
           - 12.x
           - 14.x
-          - 15.x
+          - 16.x
     steps:
     - uses: actions/checkout@v2
     - name: Use Node.js ${{ matrix.node-version }}

.github/workflows/master.yml

@@ -17,7 +17,7 @@ jobs:
         node-version:
           - 12.x
           - 14.x
-          - 15.x
+          - 16.x
     steps:
     - uses: actions/checkout@v2
     - name: Use Node.js ${{ matrix.node-version }}

.gitignore

@@ -1,4 +1,4 @@
 node_modules
 dist
 coverage
-yarn.lock
+yarn*

README.md

@@ -16,6 +16,11 @@
 Construct a `RotatedArraySet`, optionally provide a *stringify* method, converting `T` to `string` (this is not necessary for primitive types).
 
 
+## Versions
+
+ * Since v2 this is a [pure ESM][pure-esm] package, and requires Node.js >=12.20. It cannot be used from CommonJS.
+
+
 ## Example
 
 ```ts
@@ -62,3 +67,4 @@ tree.values( ); // [ [ user1, user2, user3 ] ]
 [lgtm-url]: https://lgtm.com/projects/g/grantila/rotated-array-set/context:javascript
 [node-version]: https://img.shields.io/node/v/rotated-array-set
 [node-url]: https://nodejs.org/en/
+[pure-esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c

babel.config.cjs

@@ -0,0 +1,13 @@
+module.exports = {
+	presets: [
+		[
+			'@babel/preset-env',
+			{
+				targets: {
+					node: 'current',
+				},
+			},
+		],
+		'@babel/preset-typescript',
+	],
+}

jest.config.js

@@ -9,17 +9,19 @@
   },
   "homepage": "https://github.com/grantila/rotated-array-set#readme",
   "main": "./dist/index.js",
+  "exports": "./dist/index.js",
   "types": "./dist/index.d.ts",
-  "directories": {},
+  "type": "module",
+  "sideEffects": false,
   "engines": {
-    "node": ">=12"
+    "node": "^12.20.0 || ^14.13.1 || >=16.0.0"
   },
   "files": [
     "dist"
   ],
   "scripts": {
     "build": "rimraf dist && tsc -p tsconfig.prod.json",
-    "test": "jest --coverage",
+    "test": "NODE_OPTIONS=--experimental-vm-modules jest --coverage",
     "cz": "git-cz"
   },
   "repository": {
@@ -33,17 +35,26 @@
     "arrays"
   ],
   "devDependencies": {
-    "@types/jest": "^26.0.20",
-    "@types/node": "^14.14.31",
+    "@babel/preset-env": "^7.15.6",
+    "@babel/preset-typescript": "^7.15.0",
+    "@types/jest": "^27.0.1",
+    "@types/node": "^16.9.1",
     "cz-conventional-changelog": "^3.1.0",
-    "jest": "^26.6.3",
+    "jest": "^27.1.1",
     "rimraf": "^3.0.1",
-    "ts-jest": "^26.5.2",
-    "typescript": "^4.2.2"
+    "typescript": "^4.4.3"
   },
   "config": {
     "commitizen": {
       "path": "./node_modules/cz-conventional-changelog"
     }
+  },
+  "jest": {
+    "testEnvironment": "node",
+    "coverageReporters": [
+      "lcov",
+      "text",
+      "html"
+    ]
   }
 }

package.json

@@ -10,7 +10,7 @@
 		],
 		"noEmit": true,
 		"target": "ES2019",
-		"module": "CommonJS",
+		"module": "ES2020",
 		"moduleResolution": "node",
 		"noImplicitAny": true,
 		"noUnusedLocals": true,