chore: js syntax validation in properties panel

Related to #1102

packages/form-js-editor/src/features/properties-panel/entries/JSFunctionEntry.js

@@ -107,14 +107,30 @@ function FunctionDefinition(props) {
     return get(field, path, '');
   };
 
-  const setValue = (value) => {
+  const setValue = (value, error) => {
+    if (error) {
+      return;
+    }
+
     return editField(field, path, value || '');
   };
 
+  const validate = (value) => {
+
+    try {
+      new Function(value);
+    } catch (e) {
+      return `Invalid syntax: ${e.message}`;
+    }
+
+    return null;
+  };
+
   return TextAreaEntry({
     debounce,
     element: field,
     getValue,
+    validate,
     description: 'Define the javascript function to execute.\nAccess the `data` object and use `setValue` to update the form state.',
     id,
     label: 'Javascript code',