diff --git a/CHANGELOG.md b/CHANGELOG.md
index d698399..7bbba1e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,12 @@
 
 All notable changes to this project will be documented in this file.
 
+## [1.0.4] - 31-07-23
+
+### Changed
+
+- Added `SerializationTransform` and `DataclassTransform`
+
 ## [1.0.3] - 31-07-23
 
 ### Added
diff --git a/dash_extensions/javascript.py b/dash_extensions/javascript.py
index d91b0ab..4c3c648 100644
--- a/dash_extensions/javascript.py
+++ b/dash_extensions/javascript.py
@@ -25,6 +25,11 @@ def __call__(self, var):
         return variable(*all_args)
 
     def add(self, src, name=None):
+        # Check if the function already exists.
+        for key in self.f_map:
+            if name is None and self.f_map[key] == src:
+                return key
+        # Otherwise add it.
         name = f"function{len(self.f_map)}" if name is None else name
         self.f_map[name] = src
         return name