v2.0.0: ESM/CJS dual-package, new serialization features, throwOnNonSerializable option

- Add "type": "module" with .mjs/.cjs dual-package support
- Add throwOnNonSerializable option for WeakRef, WeakMap, WeakSet, FinalizationRegistry, Promise, Generator
- Improve serialization: -0, sparse arrays, Symbol.for(), RegExp lastIndex, error subclasses, Object.create(null)
- Use dot notation in cross-ref output (___ref1.prop instead of ___ref1['prop'])
- Update @lopatnov/get-internal-type to 2.0.0
- Update CI to Node.js 18/20/22/24, tsconfig lib to ES2022
- Update README and CHANGELOG for v2.0.0
- 191 tests passing

Author: Lopatniov

.github/workflows/nodejs.yml

@@ -8,7 +8,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [18.x, 20.x, 22.x]
+        node-version: [18.x, 20.x, 22.x, 24.x]
 
     steps:
     - uses: actions/checkout@v4

.github/workflows/npmpublish.yml

@@ -11,7 +11,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: 20
+          node-version: 22
           cache: 'npm'
       - run: npm ci
       - run: npm run check
@@ -26,7 +26,7 @@ jobs:
       - run: npm run configure-npm
       - uses: actions/setup-node@v4
         with:
-          node-version: 20
+          node-version: 22
           registry-url: 'https://registry.npmjs.org'
           cache: 'npm'
       - run: npm ci
@@ -42,7 +42,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: 20
+          node-version: 22
           registry-url: 'https://npm.pkg.github.com'
           scope: '@lopatnov'
           cache: 'npm'

CHANGELOG.md

@@ -2,27 +2,51 @@
 
 All notable changes to this project will be documented in this file.
 
-## [2.0.0] - 2026-02-13
+## [2.0.0] - 2026-02-14
 
 ### Added
 
 - Cross-reference support: shared objects between different branches are now preserved as references
+- `throwOnNonSerializable` option: throws an error for non-serializable values instead of returning `"undefined"`
+- Explicit handling for non-serializable types: `Promise`, `Generator`, `WeakRef`, `WeakMap`, `WeakSet`, `FinalizationRegistry`
+- Negative zero (`-0`) preserved correctly
+- Sparse arrays preserved (holes are not filled with `undefined`)
+- `Symbol.for()` registry symbols distinguished from regular symbols
+- `Symbol("")` (empty description) distinguished from `Symbol()` (no description)
+- RegExp `lastIndex` preserved when non-zero
+- Error subclasses preserved: `TypeError`, `RangeError`, `ReferenceError`, `SyntaxError`, `URIError`, `EvalError`
+- `Object.create(null)` objects supported
+- Async functions and async generator functions supported
+- `SharedArrayBuffer` supported (grouped with `ArrayBuffer`)
+- ESM (`.mjs`) and CJS (`.cjs`) dual-package support via `exports` field
+- UMD build for browsers
+- `"type": "module"` in package.json
 - Biome for linting and formatting (replaced JSHint)
 - Jest coverage reporting enabled
-- 23 new tests for circular and cross-reference scenarios (76 total)
+- 191 tests total (up from 53)
 
 ### Fixed
 
 - **Issue #1:** Circular references to parent elements at the top level are now resolved correctly
 - Circular chain references (A -> B -> C -> A) now work at any depth
+- `counter = counter++` post-increment bug in cross-reference actions (value never incremented)
+- `Object.prototype.hasOwnProperty.call()` used instead of `value.hasOwnProperty()` to support null-prototype objects
+- Non-identifier property names in function properties now use bracket notation (`fn["my-prop"]` instead of invalid `fn.my-prop`)
+- Non-identifier property names in object literals are now quoted
+- Invalid `Date` objects now serialize as `new Date(NaN)` instead of `new Date("null")`
+- Date strings are now quoted in output
 
 ### Changed
 
+- Cross-reference output uses dot notation when possible (`___ref1.prop` instead of `___ref1['prop']`)
+- Internal IIFE variable renamed from `___j2s_` to `___ref` for readability
+- Updated `@lopatnov/get-internal-type` to 2.0.0
 - Updated all dependencies to latest versions
 - Migrated from `rollup-plugin-*` to `@rollup/plugin-*` official packages
-- Migrated CI from Node.js 12.x to Node.js 18/20/22
+- Migrated CI from Node.js 12.x to Node.js 18/20/22/24
 - Updated `@lopatnov/rollup-plugin-uglify` from 2.x to 3.x
 - Upgraded TypeScript to 5.8, Jest to 30, Rollup to 4, Biome to 2.x
+- tsconfig lib updated to ES2022
 - Minimum Node.js version is now 18.0.0
 
 ### Removed

README.md

@@ -63,6 +63,7 @@ Converts a JavaScript value to its string source code representation.
 | `nestedObjectsAmount` | `number` | `Infinity` | Max depth for nested objects |
 | `nestedArraysAmount` | `number` | `Infinity` | Max depth for nested arrays |
 | `nestedFunctionsAmount` | `number` | `Infinity` | Max depth for nested functions |
+| `throwOnNonSerializable` | `boolean` | `false` | Throw an error for non-serializable values (Promise, Generator, WeakRef, WeakMap, WeakSet, FinalizationRegistry) |
 
 ## Examples
 
@@ -121,7 +122,7 @@ var x = [1, 2, 3];
 x[0] = x;
 
 javaScriptToString(x);
-// '(function(){ var ___j2s_0 = [null, 2, 3]; ___j2s_0['0'] = ___j2s_0; return ___j2s_0; }())'
+// '(function(){ var ___ref1 = [null, 2, 3]; ___ref1[0] = ___ref1; return ___ref1; }())'
 ```
 
 ### Cross-References
@@ -133,13 +134,11 @@ var shared = { value: 42 };
 var obj = { a: shared, b: shared };
 
 javaScriptToString(obj);
-// Generates code where obj.a === obj.b (same reference), like:
-// (function(){ var ___j2s_0 = {
-// a: {
-//   value: 42
-// },
-// b: null
-// }; ___j2s_0['b'] = ___j2s_0['a']; return ___j2s_0; }())
+// Generates code where obj.a === obj.b (same reference):
+// (function(){ var ___ref1 = {
+//   a: { value: 42 },
+//   b: null
+// }; ___ref1.b = ___ref1.a; return ___ref1; }())
 ```
 
 ### Using with Web Workers
@@ -191,22 +190,29 @@ console.log(restored.name);             // "test"
 
 ## Supported Types
 
-| Type | Example |
-|------|---------|
-| Primitives | `string`, `number`, `boolean`, `undefined`, `null` |
-| BigInt | `BigInt(123)` |
-| Symbol | `Symbol("description")` |
-| RegExp | `/pattern/gi` |
-| Date | `new Date()` |
-| Error | `new Error("message")` |
-| Array | `[1, 2, 3]` |
-| Object | `{ key: "value" }` |
-| Function | `function() {}`, `() => {}` |
-| Map | `new Map([["key", "value"]])` |
-| Set | `new Set([1, 2, 3])` |
-| TypedArray | `Int8Array`, `Float64Array`, etc. |
-| ArrayBuffer | `new ArrayBuffer(8)` |
-| DataView | `new DataView(buffer)` |
+| Type | Example | Notes |
+|------|---------|-------|
+| Primitives | `string`, `number`, `boolean`, `undefined`, `null` | Including `-0` and `NaN` |
+| BigInt | `BigInt(123)` | |
+| Symbol | `Symbol("desc")`, `Symbol.for("key")` | Registry symbols preserved |
+| RegExp | `/pattern/gi` | `lastIndex` preserved when non-zero |
+| Date | `new Date("...")` | Invalid dates → `new Date(NaN)` |
+| Error | `new Error()`, `new TypeError()` | TypeError, RangeError, ReferenceError, SyntaxError, URIError, EvalError |
+| Array | `[1, 2, 3]` | Sparse arrays preserved |
+| Object | `{ key: "value" }` | Including `Object.create(null)` |
+| Function | `function() {}`, `() => {}`, `async function() {}` | Properties and prototype included |
+| Generator Function | `function*() {}`, `async function*() {}` | |
+| Map | `new Map([["key", "value"]])` | |
+| Set | `new Set([1, 2, 3])` | |
+| TypedArray | `Int8Array`, `Float64Array`, etc. | |
+| ArrayBuffer | `new ArrayBuffer(8)`, `SharedArrayBuffer` | |
+| DataView | `new DataView(buffer)` | |
+
+### Non-serializable Types
+
+The following types cannot be serialized and return `"undefined"` by default. Use `throwOnNonSerializable: true` to throw an error instead:
+
+`Promise`, `Generator`, `WeakRef`, `WeakMap`, `WeakSet`, `FinalizationRegistry`
 
 ## Demo
 

dist/javascripttostring.es5.mjs.map

@@ -1,19 +1,26 @@
-var types = {}, typesToString = types.toString, buildInList = [
+const types = {};
+const typesToString = Object.prototype.toString;
+const builtInList = [
     "Boolean",
     "Number",
     "String",
-    "Function",
     "Array",
     "Date",
     "RegExp",
     "Object",
     "Error",
     "Promise",
-    "Generator",
-    "GeneratorFunction",
-    "ArrayBuffer",
-    "DataView"
-], typedArrays = [
+    "DataView",
+    "WeakRef",
+    "FinalizationRegistry"
+];
+const functions = ["Function", "AsyncFunction"];
+const generators = ["Generator", "AsyncGenerator"];
+const generatorFunctions = ["GeneratorFunction", "AsyncGeneratorFunction"];
+const arrayBuffers = ["ArrayBuffer", "SharedArrayBuffer"];
+const maps = ["Map", "WeakMap"];
+const sets = ["Set", "WeakSet"];
+const typedArrays = [
     "Int8Array",
     "Uint8Array",
     "Uint8ClampedArray",
@@ -25,10 +32,22 @@ var types = {}, typesToString = types.toString, buildInList = [
     "Float64Array",
     "BigInt64Array",
     "BigUint64Array"
-], maps = ["Map", "WeakMap"], sets = ["Set", "WeakSet"];
-buildInList.forEach(function (name) {
+];
+builtInList.forEach(function (name) {
     types["[object " + name + "]"] = name.toLowerCase();
 });
+functions.forEach(function (name) {
+    types["[object " + name + "]"] = "function";
+});
+generators.forEach(function (name) {
+    types["[object " + name + "]"] = "generator";
+});
+generatorFunctions.forEach(function (name) {
+    types["[object " + name + "]"] = "generatorfunction";
+});
+arrayBuffers.forEach(function (name) {
+    types["[object " + name + "]"] = "arraybuffer";
+});
 maps.forEach(function (name) {
     types["[object " + name + "]"] = "map";
 });
@@ -359,8 +378,20 @@ function stringify(value, options, history) {
         case "typedarray":
             return typedArrayToString(value, options, history);
         case "set":
+            if (value instanceof WeakSet) {
+                if (options.throwOnNonSerializable) {
+                    throw new Error("Non-serializable value: WeakSet");
+                }
+                return "undefined";
+            }
             return setToString(value, options, history);
         case "map":
+            if (value instanceof WeakMap) {
+                if (options.throwOnNonSerializable) {
+                    throw new Error("Non-serializable value: WeakMap");
+                }
+                return "undefined";
+            }
             return mapToString(value, options, history);
         case "object":
             return objectToString(value, options, history);
@@ -373,6 +404,13 @@ function stringify(value, options, history) {
             return dataViewToString(value, options, history);
         case "promise":
         case "generator":
+        case "weakref":
+        case "weakmap":
+        case "weakset":
+        case "finalizationregistry":
+            if (options.throwOnNonSerializable) {
+                throw new Error(`Non-serializable value: ${getInternalType(value)}`);
+            }
             return "undefined";
         default:
             return JSON.stringify(value);
@@ -476,6 +514,7 @@ function javaScriptToString(value, options) {
         nestedObjectsAmount: options.nestedObjectsAmount === undefined ? Number.POSITIVE_INFINITY : options.nestedObjectsAmount,
         nestedArraysAmount: options.nestedArraysAmount === undefined ? Number.POSITIVE_INFINITY : options.nestedArraysAmount,
         nestedFunctionsAmount: options.nestedFunctionsAmount === undefined ? Number.POSITIVE_INFINITY : options.nestedFunctionsAmount,
+        throwOnNonSerializable: options.throwOnNonSerializable === undefined ? false : options.throwOnNonSerializable,
     };
     // Clear global state before conversion
     refs = [];
@@ -498,4 +537,4 @@ function javaScriptToString(value, options) {
 }
 
 export { javaScriptToString as default };
-//# sourceMappingURL=javascripttostring.es5.mjs.map
+//# sourceMappingURL=javascripttostring.esm.mjs.map