Convert to TypeScript and ensure strict type safety

.eslintrc.json

@@ -5,11 +5,18 @@
         "node": true,
         "jest": true
     },
-    "extends": "eslint:recommended",
+    "extends": [
+        "eslint:recommended",
+        "plugin:@typescript-eslint/recommended" // Use recommended rules from the @typescript-eslint/eslint-plugin
+    ],
+    "parser": "@typescript-eslint/parser", // Specifies the ESLint parser
     "parserOptions": {
         "ecmaVersion": 12,
-        "sourceType": "module"
+        "sourceType": "module",
+        "project": "./tsconfig.json" // Specify it only if you want to use TypeScript specific linting rules
     },
-    "rules": {
-    }
+    "plugins": [
+        "@typescript-eslint" // Use the TypeScript plugin
+    ],
+    "rules": {}
 }

.npmignore

@@ -0,0 +1,5 @@
+node_modules/
+coverage
+npm-debug.log
+yarn-error.log
+dist-es

jest.config.js

@@ -0,0 +1,4 @@
+export default {
+    preset: "ts-jest",
+    testEnvironment: "node",
+};

package.json

@@ -1,59 +1,53 @@
 {
-  "name": "deep-object-diff",
-  "version": "1.1.9",
-  "description": "Deep diffs two objects, including nested structures of arrays and objects, and return the difference.",
-  "main": "cjs/index.js",
-  "module": "mjs/index.js",
-  "exports": {
-    ".": {
-      "import": "./mjs/index.js",
-      "require": "./cjs/index.js",
-      "types": "./index.d.ts"
-    }
-  },
-  "types": "./index.d.ts",
-  "scripts": {
-    "build": "rm -rf dist && babel src -d dist/cjs && node scripts/build.mjs",
-    "prepublish": "yarn build",
-    "lint": "eslint src",
-    "test": "jest",
-    "test:coverage": "yarn test --coverage",
-    "test:watch": "yarn test -- --watch"
-  },
-  "author": "Matt Phillips",
-  "license": "MIT",
-  "devDependencies": {
-    "@babel/cli": "^7.16.8",
-    "@babel/core": "^7.16.12",
-    "@babel/preset-env": "^7.16.11",
-    "babel-jest": "^27.4.6",
-    "eslint": "^8.7.0",
-    "jest": "^27.4.7"
-  },
-  "babel": {
-    "presets": [
-      [
-        "@babel/preset-env",
-        {
-          "targets": {
-            "node": "12"
-          }
+    "name": "deep-object-diff",
+    "version": "1.2.0",
+    "description": "Deep diffs two objects, including nested structures of arrays and objects, and return the difference.",
+    "main": "./dist/cjs/index.js",
+    "module": "./dist/mjs/index.js",
+    "type": "module",
+    "exports": {
+        ".": {
+            "import": {
+                "types": "./dist/mjs/index.d.ts",
+                "default": "./dist/mjs/index.js"
+            },
+            "require": {
+                "types": "./dist/cjs/index.d.ts",
+                "default": "./dist/cjs/index.js"
+            }
         }
-      ]
-    ]
-  },
-  "repository": {
-    "type": "git",
-    "url": "git+https://github.com/mattphillips/deep-object-diff.git"
-  },
-  "keywords": [
-    "diff",
-    "object",
-    "deep",
-    "difference"
-  ],
-  "bugs": {
-    "url": "https://github.com/mattphillips/deep-object-diff/issues"
-  },
-  "homepage": "https://github.com/mattphillips/deep-object-diff#readme"
+    },
+    "scripts": {
+        "build": "rm -rf dist && tsc -p tsconfig.cjs.json && tsc -p tsconfig.mjs.json && node ./scripts/build.js",
+        "prepare": "npm run build",
+        "lint": "eslint src",
+        "test": "jest",
+        "test:coverage": "npm test -- --coverage",
+        "test:watch": "npm test -- --watch"
+    },
+    "author": "Matt Phillips",
+    "license": "MIT",
+    "devDependencies": {
+        "@types/jest": "^29.5.12",
+        "@typescript-eslint/eslint-plugin": "^7.1.0",
+        "@typescript-eslint/parser": "^7.1.0",
+        "eslint": "^8.7.0",
+        "jest": "^29.1.2",
+        "ts-jest": "^29.1.2",
+        "typescript": "^5.3.3"
+    },
+    "repository": {
+        "type": "git",
+        "url": "git+https://github.com/mattphillips/deep-object-diff.git"
+    },
+    "keywords": [
+        "diff",
+        "object",
+        "deep",
+        "difference"
+    ],
+    "bugs": {
+        "url": "https://github.com/mattphillips/deep-object-diff/issues"
+    },
+    "homepage": "https://github.com/mattphillips/deep-object-diff#readme"
 }

scripts/build.js

@@ -0,0 +1,36 @@
+import * as path from "path";
+import * as fs from "fs";
+
+const DIST = "dist";
+const MJS = "mjs";
+const CJS = "cjs";
+const PKG = "package.json";
+const FILES = ["README.md", "LICENSE"];
+
+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)
+);
+
+// Inside the MJS folder we need to replace all import x from "y" with import x
+// from "y.js"
+fs.readdirSync(path.join(DIST, MJS)).forEach((file) => {
+    const content = fs
+        .readFileSync(path.join(DIST, MJS, file), "utf-8")
+        .replace(/from "([^"]+)"/g, 'from "$1.js"');
+    fs.writeFileSync(path.join(DIST, MJS, file), content);
+});
+
+const pkg = fs.readFileSync(PKG, "utf-8");
+const json = JSON.parse(pkg);
+
+delete json.scripts;
+delete json.devDependencies;
+
+fs.writeFileSync(path.join(DIST, PKG), JSON.stringify(json, null, 2));
+
+FILES.forEach((file) => fs.copyFileSync(file, path.join(DIST, file)));

src/added.ts

@@ -0,0 +1,35 @@
+import type { DiffAddedType } from "./types";
+import {
+    isEmpty,
+    isObject,
+    hasOwnProperty,
+    makeObjectWithoutPrototype,
+} from "./utils";
+
+const addedDiff = <T, U>(lhs: T, rhs: U): DiffAddedType<T, U> => {
+    if (
+        (lhs as unknown) === (rhs as unknown) ||
+        !isObject(lhs) ||
+        !isObject(rhs)
+    )
+        return {} as DiffAddedType<T, U>;
+
+    return Object.keys(rhs).reduce((acc, key) => {
+        if (hasOwnProperty(lhs, key)) {
+            const difference = addedDiff(
+                (lhs as Record<string, unknown>)[key],
+                (rhs as Record<string, unknown>)[key]
+            );
+
+            if (isObject(difference) && isEmpty(difference)) return acc;
+
+            acc[key] = difference;
+            return acc;
+        }
+
+        acc[key] = (rhs as Record<string, unknown>)[key];
+        return acc;
+    }, makeObjectWithoutPrototype()) as DiffAddedType<T, U>;
+};
+
+export default addedDiff;