diff --git a/.eslintrc.json b/.eslintrc.json
index 41f516b..421675b 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -1,24 +1,11 @@
 
 {
     "root": true,
-    "parser": "@typescript-eslint/parser",
     "parserOptions": {
-        "ecmaVersion": 6,
+        "ecmaVersion": "latest",
         "sourceType": "module"
     },
-    "plugins": [
-        "@typescript-eslint"
-    ],
     "rules": {
-        "@typescript-eslint/naming-convention": [
-            "warn",
-            {
-                "selector": "typeLike",
-                "format": [
-                    "PascalCase"
-                ]
-            }
-        ],
         "@typescript-eslint/semi": "warn",
         "curly": "warn",
         "eqeqeq": "warn",
@@ -27,5 +14,25 @@
         "no-unused-expressions": "warn",
         "no-duplicate-imports": "warn",
         "new-parens": "warn"
-    }
-}
\ No newline at end of file
+    },
+    "overrides": [
+        {
+            "files": ["*.ts"],
+            "plugins": [
+                "@typescript-eslint"
+            ],
+            "parser": "@typescript-eslint/parser",
+            "rules": {
+                "@typescript-eslint/naming-convention": [
+                    "warn",
+                    {
+                        "selector": "typeLike",
+                        "format": [
+                            "PascalCase"
+                        ]
+                    }
+                ]
+            }
+        }
+    ]
+}
diff --git a/.mocharc.json b/.mocharc.json
index 0411c77..df902d0 100644
--- a/.mocharc.json
+++ b/.mocharc.json
@@ -1,4 +1,8 @@
 {
     "ui": "tdd",
-    "color": true
-}
\ No newline at end of file
+    "color": true,
+    "spec": [
+        "./lib/cjs/test/*.test.js",
+        "./lib/esm/test/*.test.js"
+    ]
+}
diff --git a/build/fix-esm.mjs b/build/fix-esm.mjs
new file mode 100755
index 0000000..6baccd1
--- /dev/null
+++ b/build/fix-esm.mjs
@@ -0,0 +1,12 @@
+#!/usr/bin/env node
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import fs from 'fs/promises';
+
+await fs.writeFile(
+	new URL('../lib/esm/package.json', import.meta.url),
+	JSON.stringify({ type: 'module' }, undefined, 2) + '\n'
+);
diff --git a/build/remove-sourcemap-refs.js b/build/remove-sourcemap-refs.js
index 89a0997..195cc03 100644
--- a/build/remove-sourcemap-refs.js
+++ b/build/remove-sourcemap-refs.js
@@ -15,13 +15,13 @@ function deleteRefs(dir) {
 			deleteRefs(filePath);
 		} else if (path.extname(file) === '.js') {
 			const content = fs.readFileSync(filePath, 'utf8');
-			const newContent = content.replace(/\/\/\# sourceMappingURL=[^]+.js.map/, '')
+			const newContent = content.replace(/\/\/\# sourceMappingURL=[^]+.js.map/, '');
 			if (content.length !== newContent.length) {
 				console.log('remove sourceMappingURL in ' + filePath);
 				fs.writeFileSync(filePath, newContent);
 			}
 		} else if (path.extname(file) === '.map') {
-			fs.unlinkSync(filePath)
+			fs.unlinkSync(filePath);
 			console.log('remove ' + filePath);
 		}
 	}
diff --git a/package.json b/package.json
index da7a76b..250d69b 100644
--- a/package.json
+++ b/package.json
@@ -2,9 +2,14 @@
   "name": "jsonc-parser",
   "version": "3.2.1",
   "description": "Scanner and parser for JSON with comments.",
-  "main": "./lib/umd/main.js",
-  "typings": "./lib/umd/main.d.ts",
-  "module": "./lib/esm/main.js",
+  "main": "./lib/cjs/main.js",
+  "exports": {
+    ".": {
+      "import": "./lib/esm/main.js",
+      "module": "./lib/esm/main.js",
+      "default": "./lib/cjs/main.js"
+    }
+  },
   "author": "Microsoft Corporation",
   "repository": {
     "type": "git",
@@ -25,13 +30,12 @@
     "rimraf": "^5.0.5"
   },
   "scripts": {
-    "prepack": "npm run clean && npm run compile-esm && npm run test && npm run remove-sourcemap-refs",
-    "compile": "tsc -p ./src && npm run lint",
-    "compile-esm": "tsc -p ./src/tsconfig.esm.json",
+    "prepack": "npm run clean && npm run test && npm run remove-sourcemap-refs",
+    "compile": "tsc -b && node ./build/fix-esm.mjs && npm run lint",
     "remove-sourcemap-refs": "node ./build/remove-sourcemap-refs.js",
     "clean": "rimraf lib",
-    "watch": "tsc -w -p ./src",
-    "test": "npm run compile && mocha ./lib/umd/test",
-    "lint": "eslint src/**/*.ts"
+    "watch": "tsc -w -b",
+    "test": "npm run compile && mocha",
+    "lint": "eslint ."
   }
 }
diff --git a/src/impl/edit.ts b/src/impl/edit.ts
index e810c6b..4ce554c 100644
--- a/src/impl/edit.ts
+++ b/src/impl/edit.ts
@@ -4,9 +4,9 @@
  *--------------------------------------------------------------------------------------------*/
 'use strict';
 
-import { Edit, ParseError, Node, JSONPath, Segment, ModificationOptions } from '../main';
-import { format, isEOL } from './format';
-import { parseTree, findNodeAtLocation } from './parser';
+import { Edit, ParseError, Node, JSONPath, Segment, ModificationOptions } from '../main.js';
+import { format, isEOL } from './format.js';
+import { parseTree, findNodeAtLocation } from './parser.js';
 
 export function removeProperty(text: string, path: JSONPath, options: ModificationOptions): Edit[] {
 	return setProperty(text, path, void 0, options);
diff --git a/src/impl/format.ts b/src/impl/format.ts
index 383f2fb..e9081fb 100644
--- a/src/impl/format.ts
+++ b/src/impl/format.ts
@@ -4,9 +4,9 @@
  *--------------------------------------------------------------------------------------------*/
 'use strict';
 
-import { Range, FormattingOptions, Edit, SyntaxKind, ScanError } from '../main';
-import { createScanner } from './scanner';
-import { cachedSpaces, cachedBreakLinesWithSpaces, supportedEols, SupportedEOL } from './string-intern';
+import { Range, FormattingOptions, Edit, SyntaxKind, ScanError } from '../main.js';
+import { createScanner } from './scanner.js';
+import { cachedSpaces, cachedBreakLinesWithSpaces, supportedEols, SupportedEOL } from './string-intern.js';
 
 export function format(documentText: string, range: Range | undefined, options: FormattingOptions): Edit[] {
 	let initialIndentLevel: number;
diff --git a/src/impl/parser.ts b/src/impl/parser.ts
index 3680431..c6f0666 100644
--- a/src/impl/parser.ts
+++ b/src/impl/parser.ts
@@ -4,7 +4,7 @@
  *--------------------------------------------------------------------------------------------*/
 'use strict';
 
-import { createScanner } from './scanner';
+import { createScanner } from './scanner.js';
 import {
 	JSONPath,
 	JSONVisitor,
@@ -17,7 +17,7 @@ import {
 	ScanError,
 	Segment,
 	SyntaxKind
-} from '../main';
+} from '../main.js';
 
 namespace ParseOptions {
 	export const DEFAULT = {
diff --git a/src/impl/scanner.ts b/src/impl/scanner.ts
index 8ef32f9..5422a4e 100644
--- a/src/impl/scanner.ts
+++ b/src/impl/scanner.ts
@@ -4,7 +4,7 @@
  *--------------------------------------------------------------------------------------------*/
 'use strict';
 
-import { ScanError, SyntaxKind, JSONScanner } from '../main';
+import { ScanError, SyntaxKind, JSONScanner } from '../main.js';
 
 /**
  * Creates a JSON scanner on the given text.
diff --git a/src/main.ts b/src/main.ts
index 9852b67..44b5a7f 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -4,10 +4,10 @@
  *--------------------------------------------------------------------------------------------*/
 'use strict';
 
-import * as formatter from './impl/format';
-import * as edit from './impl/edit';
-import * as scanner from './impl/scanner';
-import * as parser from './impl/parser';
+import * as formatter from './impl/format.js';
+import * as edit from './impl/edit.js';
+import * as scanner from './impl/scanner.js';
+import * as parser from './impl/parser.js';
 
 /**
  * Creates a JSON scanner on the given text.
diff --git a/src/test/edit.test.ts b/src/test/edit.test.ts
index 2e011de..c2f0cda 100644
--- a/src/test/edit.test.ts
+++ b/src/test/edit.test.ts
@@ -5,18 +5,18 @@
 'use strict';
 
 import * as assert from 'assert';
-import { FormattingOptions, Edit, ModificationOptions, modify } from '../main';
+import { FormattingOptions, Edit, ModificationOptions, modify } from '../main.js';
 
 suite('JSON - edits', () => {
 
 	function assertEdit(content: string, edits: Edit[], expected: string) {
-		assert(edits);
+		assert.ok(edits);
 		let lastEditOffset = content.length;
 		for (let i = edits.length - 1; i >= 0; i--) {
 			let edit = edits[i];
-			assert(edit.offset >= 0 && edit.length >= 0 && edit.offset + edit.length <= content.length);
-			assert(typeof edit.content === 'string');
-			assert(lastEditOffset >= edit.offset + edit.length); // make sure all edits are ordered
+			assert.ok(edit.offset >= 0 && edit.length >= 0 && edit.offset + edit.length <= content.length);
+			assert.ok(typeof edit.content === 'string');
+			assert.ok(lastEditOffset >= edit.offset + edit.length); // make sure all edits are ordered
 			lastEditOffset = edit.offset;
 			content = content.substring(0, edit.offset) + edit.content + content.substring(edit.offset + edit.length);
 		}
diff --git a/src/test/format.test.ts b/src/test/format.test.ts
index c3a7b45..b8ec119 100644
--- a/src/test/format.test.ts
+++ b/src/test/format.test.ts
@@ -5,8 +5,8 @@
 'use strict';
 
 import * as assert from 'assert';
-import * as Formatter from '../impl/format';
-import { Range } from '../main';
+import * as Formatter from '../impl/format.js';
+import { Range } from '../main.js';
 
 suite('JSON - formatter', () => {
 
@@ -25,9 +25,9 @@ suite('JSON - formatter', () => {
 
 		for (let i = edits.length - 1; i >= 0; i--) {
 			const edit = edits[i];
-			// assert(edit.offset >= 0 && edit.length >= 0 && edit.offset + edit.length <= content.length);
-			// assert(typeof edit.content === 'string');
-			// assert(lastEditOffset >= edit.offset + edit.length); // make sure all edits are ordered
+			// assert.ok(edit.offset >= 0 && edit.length >= 0 && edit.offset + edit.length <= content.length);
+			// assert.ok(typeof edit.content === 'string');
+			// assert.ok(lastEditOffset >= edit.offset + edit.length); // make sure all edits are ordered
 			lastEditOffset = edit.offset;
 			content = content.substring(0, edit.offset) + edit.content + content.substring(edit.offset + edit.length);
 		}
diff --git a/src/test/json.test.ts b/src/test/json.test.ts
index 4cf15c9..e647e62 100644
--- a/src/test/json.test.ts
+++ b/src/test/json.test.ts
@@ -8,7 +8,7 @@ import * as assert from 'assert';
 import {
 	SyntaxKind, createScanner, parse, getLocation, Node, ParseError, parseTree, ParseErrorCode,
 	ParseOptions, Segment, findNodeAtLocation, getNodeValue, getNodePath, ScanError, visit, JSONVisitor, JSONPath
-} from '../main';
+} from '../main.js';
 
 function assertKinds(text: string, ...kinds: SyntaxKind[]): void {
 	var scanner = createScanner(text);
@@ -43,7 +43,7 @@ function assertInvalidParse(input: string, expected: any, options?: ParseOptions
 	var errors: ParseError[] = [];
 	var actual = parse(input, errors, options);
 
-	assert(errors.length > 0);
+	assert.ok(errors.length > 0);
 	assert.deepStrictEqual(actual, expected);
 }
 
@@ -117,7 +117,7 @@ function assertLocation(input: string, expectedSegments: Segment[], expectedNode
 	var offset = input.indexOf('|');
 	input = input.substring(0, offset) + input.substring(offset + 1, input.length);
 	var actual = getLocation(input, offset);
-	assert(actual);
+	assert.ok(actual);
 	assert.deepStrictEqual(actual.path, expectedSegments, input);
 	assert.strictEqual(actual.previousNode && actual.previousNode.type, expectedNodeType, input);
 	assert.strictEqual(actual.isAtPropertyKey, expectedCompleteProperty, input);
@@ -127,7 +127,7 @@ function assertMatchesLocation(input: string, matchingSegments: Segment[], expec
 	var offset = input.indexOf('|');
 	input = input.substring(0, offset) + input.substring(offset + 1, input.length);
 	var actual = getLocation(input, offset);
-	assert(actual);
+	assert.ok(actual);
 	assert.strictEqual(actual.matches(matchingSegments), expectedResult);
 }
 
diff --git a/src/tsconfig.json b/src/tsconfig.json
deleted file mode 100644
index d399fcb..0000000
--- a/src/tsconfig.json
+++ /dev/null
@@ -1,16 +0,0 @@
-{
-	"compilerOptions": {
-		"target": "es2020",
-		"module": "umd",
-		"moduleResolution": "node",
-		"sourceMap": true,
-		"declaration": true,
-		"stripInternal": true,
-		"outDir": "../lib/umd",
-		"strict": true,
-		"preserveConstEnums": true,
-		"lib": [
-			"es2020"
-		]
-	}
-}
\ No newline at end of file
diff --git a/tsconfig.cjs.json b/tsconfig.cjs.json
new file mode 100644
index 0000000..d9c0b81
--- /dev/null
+++ b/tsconfig.cjs.json
@@ -0,0 +1,7 @@
+{
+	"extends": "./tsconfig.esm.json",
+	"compilerOptions": {
+		"module": "commonjs",
+		"outDir": "./lib/cjs"
+	}
+}
diff --git a/src/tsconfig.esm.json b/tsconfig.esm.json
similarity index 60%
rename from src/tsconfig.esm.json
rename to tsconfig.esm.json
index 8c8246c..710d61d 100644
--- a/src/tsconfig.esm.json
+++ b/tsconfig.esm.json
@@ -1,16 +1,18 @@
 {
+	"include": ["src"],
 	"compilerOptions": {
 		"target": "es2020",
-		"module": "es6",
-		"moduleResolution": "node",
+		"module": "esnext",
+		"moduleResolution": "node16",
 		"sourceMap": true,
 		"declaration": true,
 		"stripInternal": true,
-		"outDir": "../lib/esm",
+		"outDir": "./lib/esm",
+		"rootDir": "./src",
 		"strict": true,
 		"preserveConstEnums": true,
 		"lib": [
 			"es2020"
 		]
 	}
-}
\ No newline at end of file
+}
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..cc45744
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,7 @@
+{
+  "files": [],
+  "references": [
+    { "path": "./tsconfig.cjs.json" },
+    { "path": "./tsconfig.esm.json" }
+  ]
+}