javascript-obfuscator · sanex3339 · Mar 22, 2026 · Mar 22, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -3,6 +3,7 @@ Change Log
 v5.4.0
 ---
 * Add support for `import attributes`. Fixes https://github.com/javascript-obfuscator/javascript-obfuscator/issues/1256
+* Add `renameProperties` support for private class fields and methods (`#foo`, `#bar()`). Fixes https://github.com/javascript-obfuscator/javascript-obfuscator/issues/1220
 * Fixed `reservedNames` not preserving class method and property names when `stringArray` or `deadCodeInjection` is enabled. Fixes https://github.com/javascript-obfuscator/javascript-obfuscator/issues/1279
 * Replaced `mkdirp` dependency with native `fs.mkdirSync({ recursive: true })`. Fixes https://github.com/javascript-obfuscator/javascript-obfuscator/issues/1275. Thank you https://github.com/roli-lpci!
 * Replaced `conf` dependency with custom implementation using `env-paths` and native `fs`

diff --git a/...es/node-transformers/rename-properties-transformers/replacer/IRenamePropertiesReplacer.ts b/...es/node-transformers/rename-properties-transformers/replacer/IRenamePropertiesReplacer.ts
@@ -7,8 +7,8 @@ export interface IRenamePropertiesReplacer {
     excludePropertyName(propertyName: string): void;
 
     /**
-     * @param {ESTree.Identifier | ESTree.Literal} node
-     * @returns {ESTree.Identifier | ESTree.Literal}
+     * @param {ESTree.Identifier | ESTree.Literal | ESTree.PrivateIdentifier} node
+     * @returns {ESTree.Identifier | ESTree.Literal | ESTree.PrivateIdentifier}
      */
-    replace(node: ESTree.Identifier | ESTree.Literal): ESTree.Identifier | ESTree.Literal;
+    replace(node: ESTree.Identifier | ESTree.Literal | ESTree.PrivateIdentifier): ESTree.Identifier | ESTree.Literal | ESTree.PrivateIdentifier;
 }
diff --git a/src/node-transformers/rename-properties-transformers/RenamePropertiesTransformer.ts b/src/node-transformers/rename-properties-transformers/RenamePropertiesTransformer.ts
@@ -48,7 +48,7 @@ export class RenamePropertiesTransformer extends AbstractNodeTransformer {
     >(
         propertyNode: TNode,
         propertyKeyNode: ESTree.Expression | ESTree.PrivateIdentifier
-    ): propertyKeyNode is ESTree.Identifier | ESTree.Literal {
+    ): propertyKeyNode is ESTree.Identifier | ESTree.Literal | ESTree.PrivateIdentifier {
         if (NodeGuards.isIdentifierNode(propertyKeyNode) && propertyNode.computed) {
             return false;
         }
@@ -111,8 +111,13 @@ export class RenamePropertiesTransformer extends AbstractNodeTransformer {
      * @param {NodeGuards} parentNode
      * @returns {Node}
      */
+    // eslint-disable-next-line complexity
     public transformNode(node: ESTree.Node, parentNode: ESTree.Node): ESTree.Node {
-        if (!NodeGuards.isIdentifierNode(node) && !NodeGuards.isLiteralNode(node)) {
+        if (
+            !NodeGuards.isIdentifierNode(node) &&
+            !NodeGuards.isLiteralNode(node) &&
+            !NodeGuards.isPrivateIdentifierNode(node)
+        ) {
             return node;
         }
 

diff --git a/src/node-transformers/rename-properties-transformers/replacer/RenamePropertiesReplacer.ts b/src/node-transformers/rename-properties-transformers/replacer/RenamePropertiesReplacer.ts
@@ -80,10 +80,14 @@ export class RenamePropertiesReplacer implements IRenamePropertiesReplacer {
     }
 
     /**
-     * @param {ESTree.Identifier | ESTree.Literal} node
-     * @returns {ESTree.Identifier | ESTree.Literal}
+     * @param {ESTree.Identifier | ESTree.Literal | ESTree.PrivateIdentifier} node
+     * @returns {ESTree.Identifier | ESTree.Literal | ESTree.PrivateIdentifier}
      */
-    public replace(node: ESTree.Identifier | ESTree.Literal): ESTree.Identifier | ESTree.Literal {
+    public replace(node: ESTree.Identifier | ESTree.Literal | ESTree.PrivateIdentifier): ESTree.Identifier | ESTree.Literal | ESTree.PrivateIdentifier {
+        if (NodeGuards.isPrivateIdentifierNode(node)) {
+            return NodeFactory.privateIdentifierNode(this.replacePropertyName(node.name));
+        }
+
         if (NodeGuards.isIdentifierNode(node)) {
             return NodeFactory.identifierNode(this.replacePropertyName(node.name));
         }

diff --git a/src/node/NodeFactory.ts b/src/node/NodeFactory.ts
@@ -373,6 +373,18 @@ export class NodeFactory {
         };
     }
 
+    /**
+     * @param {string} name
+     * @returns {PrivateIdentifier}
+     */
+    public static privateIdentifierNode(name: string): ESTree.PrivateIdentifier {
+        return {
+            type: NodeType.PrivateIdentifier,
+            name,
+            metadata: { ignoredNode: false }
+        };
+    }
+
     /**
      * @param {(ImportSpecifier | ImportDefaultSpecifier | ImportNamespaceSpecifier)[]} specifiers
      * @param {Literal} source

diff --git a/src/node/NodeMetadata.ts b/src/node/NodeMetadata.ts
@@ -49,7 +49,9 @@ export class NodeMetadata {
      * @param {Identifier | Literal} node
      * @returns {boolean}
      */
-    public static isPropertyKeyToRenameNode(node: ESTree.Identifier | ESTree.Literal): boolean {
+    public static isPropertyKeyToRenameNode(
+        node: ESTree.Identifier | ESTree.PrivateIdentifier | ESTree.Literal
+    ): boolean {
         return (
             NodeMetadata.get<ESTree.IdentifierNodeMetadata | ESTree.LiteralNodeMetadata, 'propertyKeyToRenameNode'>(
                 node,

diff --git a/test/functional-tests/javascript-obfuscator/JavaScriptObfuscator.spec.ts b/test/functional-tests/javascript-obfuscator/JavaScriptObfuscator.spec.ts
@@ -910,9 +910,7 @@ describe('JavaScriptObfuscator', () => {
         });
 
         describe('Private identifiers support', () => {
-            const regExp: RegExp = new RegExp(
-                'class Foo *{ *' + '#bar *= *0x1; *' + "\\['method'] *\\(\\) *{ *" + 'this\.#bar *= *0x2;' + '} *' + '}'
-            );
+            const variableMatch: string = '_0x([a-f0-9]){4,6}';
 
             let obfuscatedCode: string;
 
@@ -925,8 +923,20 @@ describe('JavaScriptObfuscator', () => {
                 }).getObfuscatedCode();
             });
 
-            it('should support private identifiers', () => {
-                assert.match(obfuscatedCode, regExp);
+            it('should rename private field', () => {
+                assert.match(obfuscatedCode, new RegExp(`#${variableMatch} *= *0x1`));
+            });
+
+            it('should rename private field access', () => {
+                assert.match(obfuscatedCode, new RegExp(`this\\.#${variableMatch} *= *0x2`));
+            });
+
+            it('should rename private method declaration', () => {
+                assert.match(obfuscatedCode, new RegExp(`#${variableMatch}\\(\\) *\\{`));
+            });
+
+            it('should rename private method call', () => {
+                assert.match(obfuscatedCode, new RegExp(`this\\.#${variableMatch}\\(\\)`));
             });
         });
 

diff --git a/test/functional-tests/javascript-obfuscator/fixtures/private-identifier.js b/test/functional-tests/javascript-obfuscator/fixtures/private-identifier.js
@@ -4,4 +4,13 @@ class Foo {
     method() {
         this.#bar = 2;
     }
-}
+
+    #privateMethod() {
+        return this.#bar;
+    }
+
+    run() {
+        this.method();
+        return this.#privateMethod();
+    }
+}