Add build script to configure esmodules

Author: mattphillips

package.json

@@ -2,18 +2,17 @@
   "name": "deep-object-diff",
   "version": "1.1.3",
   "description": "Deep diffs two objects, including nested structures of arrays and objects, and return the difference.",
-  "main": "dist/index.js",
-  "module": "dist-es/index.js",
+  "main": "cjs/index.js",
+  "module": "mjs/index.js",
+  "exports": {
+    ".": {
+      "import": "./cjs/index.js",
+      "require": "./mjs/index.js"
+    }
+  },
   "types": "./index.d.ts",
-  "files": [
-    "dist",
-    "dist-es",
-    "index.d.ts",
-    "README.md"
-  ],
   "scripts": {
-    "build": "babel src -d dist && yarn build:esmodule",
-    "build:esmodule": "rm -rf dist-es && mkdir dist-es && cp -r src/* dist-es &&  rm -rf dist-es/**/*.test.js",
+    "build": "rm -rf dist && babel src -d dist/cjs && node scripts/build.mjs",
     "prepublish": "yarn build",
     "lint": "eslint src",
     "test": "jest",

scripts/build.mjs

@@ -0,0 +1,26 @@
+import * as path from "path";
+import * as fs from "fs";
+
+const DIST = "dist";
+const SRC = "src";
+const MJS = "mjs";
+const CJS = "cjs";
+const PKG = "package.json";
+const FILES = ["index.d.ts", "README.md", "LICENSE"];
+
+fs.mkdirSync(path.join(DIST, MJS));
+fs.readdirSync("./src").forEach((file) => fs.copyFileSync(path.join(SRC, file), path.join(DIST, MJS, file)));
+
+fs.writeFileSync(path.join(DIST, CJS, PKG), JSON.stringify({ type: "commonjs" }, null, 2));
+fs.writeFileSync(path.join(DIST, MJS, PKG), JSON.stringify({ type: "module" }, null, 2));
+
+const pkg = fs.readFileSync(PKG, "utf-8");
+const json = JSON.parse(pkg);
+
+delete json.scripts;
+delete json.devDependencies;
+delete json.babel;
+
+fs.writeFileSync(path.join(DIST, PKG), JSON.stringify(json, null, 2));
+
+FILES.forEach((file) => fs.copyFileSync(file, path.join(DIST, file)));