debugged two issues, see details

added a missing return statement inside a map method and disabled eslinter for one line of code in useeffect.

src/api/index.js

@@ -20,10 +20,10 @@ const Api = {
                   const resProperties = responses[2];
 
                   const modifyData = (typeInfo, array) => {
-
-                    array.data.map((iteration, index) =>    {
+                      array.data.map((iteration, index) => {
                         iteration['type'] = typeInfo
                         iteration['id'] = iteration.id+'-'+typeInfo
+                        return iteration
                       })
                   }
                   modifyData('agent', resAgents);

src/components/List/index.js

@@ -16,9 +16,9 @@ function List() {
   const [checkedAgents, setCheckedAgents] = useState(true);
   const [checkedShops, setCheckedShops] = useState(true);
   const [checkedProperties, setCheckedProperties] = useState(true);
-  const [fullData, setFullData] = useState(spinnerLoadingData); //
-  const [resultList, setResultList] = useState( spinnerLoadingData );  //
-  const [filteredList, setFilteredList] = useState( spinnerLoadingData ); //
+  const [fullData, setFullData] = useState(spinnerLoadingData);
+  const [resultList, setResultList] = useState(spinnerLoadingData);
+  const [filteredList, setFilteredList] = useState(spinnerLoadingData);
   const [inputValue, setInputValue]   = useState('')
   const [listOfNames, setListOfNames] = useState([]);
   const [sorting, setSorting] = useState(false);
@@ -51,11 +51,9 @@ function List() {
 
 
   useEffect(  () => {
-     // all Three Checkboxes are checked
     if ((checkedAgents) && (checkedShops) && (checkedProperties))  {
        setFilteredList(fullData)
     }
-     // none of the three checkboxes are selected
     else if ((!checkedAgents) && (!checkedShops) && (!checkedProperties)) {
        setFilteredList({'mergedArray' :  [] })
     }
@@ -71,7 +69,10 @@ function List() {
             });
          setFilteredList({'mergedArray' :  result})
     }
-  }, [checkedAgents, checkedShops , checkedProperties, fullData.whenToUpdateProp]);
+  },
+  // alternatively to disabling the esLinter for the below line to not print a warning-message in the console, I would have to establish useReducer instead of fullData
+  // eslint-disable-next-line react-hooks/exhaustive-deps
+  [checkedAgents, checkedShops , checkedProperties, fullData.whenToUpdateProp]);