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docs/api/reactivity-utility.md

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+# Reactivity API: Utility
+
+## cleanup()
+
+Runs a callback anytime a reactive scope is re-ran.
+
+- **Type**
+
+    ```lua
+    function cleanup(callback: () -> ())
+    ```
+
+- **Example**
+
+    ```lua
+    local data = source(1)
+
+    watch(function()
+        local label = create "TextLabel" { Text = data }
+
+        cleanup(function()
+            label:Destroy()
+        end)
+    end)
+    ```