diff --git a/codeflash/languages/javascript/normalizer.py b/codeflash/languages/javascript/normalizer.py
index 39ae952cb..b42ee8057 100644
--- a/codeflash/languages/javascript/normalizer.py
+++ b/codeflash/languages/javascript/normalizer.py
@@ -1,7 +1,6 @@
 """JavaScript/TypeScript code normalizer using tree-sitter.
 
-Not currently wired into JavaScriptSupport.normalize_code — kept as a
-ready-to-use upgrade path when AST-based JS deduplication is needed.
+Wired into JavaScriptSupport.normalize_code for AST-based JS deduplication.
 
 The old CodeNormalizer ABC (deleted from base.py) is preserved below for reference.
 """
@@ -236,8 +235,7 @@ def normalize_js_code(code: str, typescript: bool = False) -> str:
     Uses tree-sitter to parse and normalize variable names. Falls back to
     basic comment/whitespace stripping if tree-sitter is unavailable or parsing fails.
 
-    Not currently wired into JavaScriptSupport.normalize_code — kept as a
-    ready-to-use upgrade path when AST-based JS deduplication is needed.
+    Wired into JavaScriptSupport.normalize_code for AST-based JS deduplication.
     """
     try:
         from codeflash.languages.javascript.treesitter import TreeSitterAnalyzer, TreeSitterLanguage
diff --git a/codeflash/languages/javascript/support.py b/codeflash/languages/javascript/support.py
index 69fd5ac96..f1a570740 100644
--- a/codeflash/languages/javascript/support.py
+++ b/codeflash/languages/javascript/support.py
@@ -1207,20 +1207,29 @@ class JavaScriptSupport:
                         return node
 
             # Check function declarations
-            if node.type in ("function_declaration", "function"):
+            if node.type in (
+                "function_declaration",
+                "function",
+                "generator_function_declaration",
+                "generator_function",
+            ):
                 name_node = node.child_by_field_name("name")
                 if name_node:
                     name = source_bytes[name_node.start_byte : name_node.end_byte].decode("utf8")
                     if name == target_name:
                         return node
 
-            # Check arrow functions assigned to variables
-            if node.type == "lexical_declaration":
+            # Check arrow functions and function expressions assigned to variables
+            if node.type in ("lexical_declaration", "variable_declaration"):
                 for child in node.children:
                     if child.type == "variable_declarator":
                         name_node = child.child_by_field_name("name")
                         value_node = child.child_by_field_name("value")
-                        if name_node and value_node and value_node.type == "arrow_function":
+                        if (
+                            name_node
+                            and value_node
+                            and value_node.type in ("arrow_function", "function_expression", "generator_function")
+                        ):
                             name = source_bytes[name_node.start_byte : name_node.end_byte].decode("utf8")
                             if name == target_name:
                                 return value_node
@@ -1235,6 +1244,7 @@ class JavaScriptSupport:
 
         func_node = find_function_node(tree.root_node, function_name)
         if not func_node:
+            logger.debug("Could not find function '%s' in optimized code for body extraction", function_name)
             return None
 
         # Find the body node
@@ -1295,14 +1305,21 @@ class JavaScriptSupport:
                     if name == target_name and (node.start_point[0] + 1) == target_line:
                         return node
 
-            if node.type == "lexical_declaration":
+            if node.type in ("lexical_declaration", "variable_declaration"):
                 for child in node.children:
                     if child.type == "variable_declarator":
                         name_node = child.child_by_field_name("name")
                         value_node = child.child_by_field_name("value")
-                        if name_node and value_node and value_node.type == "arrow_function":
+                        if (
+                            name_node
+                            and value_node
+                            and value_node.type in ("arrow_function", "function_expression", "generator_function")
+                        ):
                             name = source_bytes[name_node.start_byte : name_node.end_byte].decode("utf8")
-                            if name == target_name and (node.start_point[0] + 1) == target_line:
+                            if name == target_name and (
+                                (node.start_point[0] + 1) == target_line
+                                or (value_node.start_point[0] + 1) == target_line
+                            ):
                                 return value_node
 
             for child in node.children:
@@ -1686,26 +1703,14 @@ class JavaScriptSupport:
             return False
 
     def normalize_code(self, source: str) -> str:
-        """Normalize JavaScript code for deduplication.
+        """Normalize JavaScript code for deduplication using tree-sitter."""
+        from codeflash.languages.javascript.normalizer import normalize_js_code
 
-        Removes comments and normalizes whitespace.
-
-        Args:
-            source: Source code to normalize.
-
-        Returns:
-            Normalized source code.
-
-        """
-        # Simple normalization: remove extra whitespace
-        # A full implementation would use tree-sitter to strip comments
-        lines = source.splitlines()
-        normalized_lines = []
-        for line in lines:
-            stripped = line.strip()
-            if stripped and not stripped.startswith("//"):
-                normalized_lines.append(stripped)
-        return "\n".join(normalized_lines)
+        try:
+            is_ts = self.treesitter_language == TreeSitterLanguage.TYPESCRIPT
+            return normalize_js_code(source, typescript=is_ts)
+        except Exception:
+            return source
 
     def generate_concolic_tests(
         self, test_cfg: Any, project_root: Any, function_to_optimize: Any, function_to_optimize_ast: Any
diff --git a/tests/test_code_deduplication.py b/tests/test_code_deduplication.py
index 3cb266785..c4a826330 100644
--- a/tests/test_code_deduplication.py
+++ b/tests/test_code_deduplication.py
@@ -1,3 +1,4 @@
+from codeflash.languages.javascript.normalizer import normalize_js_code
 from codeflash.languages.python.normalizer import normalize_python_code as normalize_code
 
 
@@ -133,3 +134,74 @@ def safe_divide(a, b):
     assert normalize_code(code9) == normalize_code(code10)
 
     assert normalize_code(code9) != normalize_code(code8)
+
+
+# === JavaScript deduplication tests ===
+
+
+def test_js_deduplicate_same_logic_different_vars():
+    code1 = """
+function process(items) {
+    const result = [];
+    for (const item of items) {
+        result.push(item * 2);
+    }
+    return result;
+}
+"""
+    code2 = """
+function process(items) {
+    const output = [];
+    for (const val of items) {
+        output.push(val * 2);
+    }
+    return output;
+}
+"""
+    assert normalize_js_code(code1) == normalize_js_code(code2)
+
+
+def test_js_different_logic_not_deduplicated():
+    code1 = """
+function compute(x) {
+    return x + 1;
+}
+"""
+    code2 = """
+function compute(x) {
+    return x * 2;
+}
+"""
+    assert normalize_js_code(code1) != normalize_js_code(code2)
+
+
+def test_js_deduplicate_whitespace_and_comments():
+    code1 = """
+function add(a, b) {
+    // fast path
+    return a + b;
+}
+"""
+    code2 = """
+function add(a, b) {
+    /* optimized */
+    return a + b;
+}
+"""
+    assert normalize_js_code(code1) == normalize_js_code(code2)
+
+
+def test_ts_normalize():
+    code1 = """
+function greet(name: string): string {
+    const msg = "hello " + name;
+    return msg;
+}
+"""
+    code2 = """
+function greet(name: string): string {
+    const result = "hello " + name;
+    return result;
+}
+"""
+    assert normalize_js_code(code1, typescript=True) == normalize_js_code(code2, typescript=True)
diff --git a/tests/test_languages/test_javascript_support.py b/tests/test_languages/test_javascript_support.py
index 800e01a29..5d5943151 100644
--- a/tests/test_languages/test_javascript_support.py
+++ b/tests/test_languages/test_javascript_support.py
@@ -443,10 +443,10 @@ function add(a, b {
 
 
 class TestNormalizeCode:
-    """Tests for normalize_code method."""
+    """Tests for normalize_code method using tree-sitter normalizer."""
 
     def test_removes_comments(self, js_support):
-        """Test that single-line comments are removed."""
+        """Test that comments are absent from normalized output."""
         code = """
 function add(a, b) {
     // Add two numbers
@@ -455,19 +455,43 @@ function add(a, b) {
 """
         normalized = js_support.normalize_code(code)
         assert "// Add two numbers" not in normalized
-        assert "return a + b" in normalized
+        assert "Add two numbers" not in normalized
 
-    def test_preserves_functionality(self, js_support):
-        """Test that code functionality is preserved."""
-        code = """
-function add(a, b) {
-    // Comment
-    return a + b;
+    def test_same_logic_different_vars_are_equal(self, js_support):
+        """Test that two functions with same logic but different variable names normalize identically."""
+        code1 = """
+function process(items) {
+    const result = [];
+    for (const item of items) {
+        result.push(item * 2);
+    }
+    return result;
 }
 """
-        normalized = js_support.normalize_code(code)
-        assert "function add" in normalized
-        assert "return" in normalized
+        code2 = """
+function process(items) {
+    const output = [];
+    for (const val of items) {
+        output.push(val * 2);
+    }
+    return output;
+}
+"""
+        assert js_support.normalize_code(code1) == js_support.normalize_code(code2)
+
+    def test_different_logic_not_equal(self, js_support):
+        """Test that two functions with different logic produce different normalized forms."""
+        code1 = """
+function compute(x) {
+    return x + 1;
+}
+"""
+        code2 = """
+function compute(x) {
+    return x * 2;
+}
+"""
+        assert js_support.normalize_code(code1) != js_support.normalize_code(code2)
 
 
 class TestExtractCodeContext:
diff --git a/tests/test_languages/test_js_code_replacer.py b/tests/test_languages/test_js_code_replacer.py
index 5ed2a903f..8ff333ad4 100644
--- a/tests/test_languages/test_js_code_replacer.py
+++ b/tests/test_languages/test_js_code_replacer.py
@@ -15,7 +15,7 @@ from pathlib import Path
 
 import pytest
 
-from codeflash.languages.base import Language
+from codeflash.languages.base import FunctionFilterCriteria, Language
 from codeflash.languages.code_replacer import replace_function_definitions_for_language
 from codeflash.languages.current import set_current_language
 from codeflash.languages.javascript.module_system import (
@@ -2264,3 +2264,150 @@ export function processNode(node: TreeNode, space: NodeSpace): number {
         assert "// Optimized" in result
 
         assert ts_support.validate_syntax(result) is True
+
+
+class TestVariableAssignedFunctionReplacement:
+    """Tests for replacing functions assigned to variables (function expressions, var declarations, etc.)."""
+
+    NO_EXPORT_FILTER = FunctionFilterCriteria(require_export=False, require_return=False)
+
+    def test_replace_function_expression_body(self, js_support, temp_project):
+        """Test replacing an exported const-assigned function expression."""
+        original_source = """\
+export const foo = function(x) {
+    return x + 1;
+};
+"""
+        file_path = temp_project / "funcs.js"
+        file_path.write_text(original_source, encoding="utf-8")
+
+        source = file_path.read_text(encoding="utf-8")
+        functions = js_support.discover_functions(source, file_path)
+        assert len(functions) == 1
+        func = functions[0]
+        assert func.function_name == "foo"
+
+        optimized_code = """\
+export const foo = function(x) {
+    return (x + 1) | 0;
+};
+"""
+
+        result = js_support.replace_function(original_source, func, optimized_code)
+
+        assert "return (x + 1) | 0;" in result
+        assert js_support.validate_syntax(result) is True
+
+    def test_replace_function_expression_with_var(self, js_support, temp_project):
+        """Test replacing a var-assigned function expression (non-exported, e.g. CommonJS)."""
+        original_source = """\
+var foo = function(x) {
+    return x * 2;
+};
+"""
+        file_path = temp_project / "funcs.js"
+        file_path.write_text(original_source, encoding="utf-8")
+
+        source = file_path.read_text(encoding="utf-8")
+        functions = js_support.discover_functions(source, file_path, filter_criteria=self.NO_EXPORT_FILTER)
+        assert len(functions) == 1
+        func = functions[0]
+        assert func.function_name == "foo"
+
+        optimized_code = """\
+var foo = function(x) {
+    return x << 1;
+};
+"""
+
+        result = js_support.replace_function(original_source, func, optimized_code)
+
+        assert "return x << 1;" in result
+        assert js_support.validate_syntax(result) is True
+
+    def test_replace_generator_function_expression(self, js_support, temp_project):
+        """Test replacing an exported const-assigned generator function expression."""
+        original_source = """\
+export const gen = function*(n) {
+    for (let i = 0; i < n; i++) {
+        yield i;
+    }
+};
+"""
+        file_path = temp_project / "generators.js"
+        file_path.write_text(original_source, encoding="utf-8")
+
+        source = file_path.read_text(encoding="utf-8")
+        functions = js_support.discover_functions(source, file_path, filter_criteria=self.NO_EXPORT_FILTER)
+        assert len(functions) == 1
+        func = functions[0]
+        assert func.function_name == "gen"
+
+        optimized_code = """\
+export const gen = function*(n) {
+    let i = 0;
+    while (i < n) yield i++;
+};
+"""
+
+        result = js_support.replace_function(original_source, func, optimized_code)
+
+        assert "while (i < n) yield i++;" in result
+        assert js_support.validate_syntax(result) is True
+
+    def test_replace_arrow_function_multiline_declaration(self, js_support, temp_project):
+        """Test replacing an arrow function where the arrow is on a different line than const."""
+        original_source = """\
+export const calculate =
+    (a, b) => {
+        return a + b;
+    };
+"""
+        file_path = temp_project / "calc.js"
+        file_path.write_text(original_source, encoding="utf-8")
+
+        source = file_path.read_text(encoding="utf-8")
+        functions = js_support.discover_functions(source, file_path)
+        assert len(functions) == 1
+        func = functions[0]
+        assert func.function_name == "calculate"
+
+        optimized_code = """\
+export const calculate =
+    (a, b) => {
+        return (a + b) | 0;
+    };
+"""
+
+        result = js_support.replace_function(original_source, func, optimized_code)
+
+        assert "return (a + b) | 0;" in result
+        assert js_support.validate_syntax(result) is True
+
+    def test_replace_async_arrow_function(self, js_support, temp_project):
+        """Test replacing an exported const-assigned async arrow function."""
+        original_source = """\
+export const fetchData = async (url) => {
+    const response = await fetch(url);
+    return response.json();
+};
+"""
+        file_path = temp_project / "api.js"
+        file_path.write_text(original_source, encoding="utf-8")
+
+        source = file_path.read_text(encoding="utf-8")
+        functions = js_support.discover_functions(source, file_path)
+        assert len(functions) == 1
+        func = functions[0]
+        assert func.function_name == "fetchData"
+
+        optimized_code = """\
+export const fetchData = async (url) => {
+    return (await fetch(url)).json();
+};
+"""
+
+        result = js_support.replace_function(original_source, func, optimized_code)
+
+        assert "return (await fetch(url)).json();" in result
+        assert js_support.validate_syntax(result) is True