Only allow to click submit button if validation is correct

frontend/src/components/pages/Umfrage.js

@@ -14,6 +14,7 @@ export default function Umfrage() {
   const [skills, setSkills] = useState("");
 
   let surveyIsValid = true;
+  let errorMessage = ""
 
   const onSubmitClick = (e) => {
     e.preventDefault();
@@ -25,30 +26,33 @@ export default function Umfrage() {
     };
 
     if (!Number(age)) {
-      console.log("age is not a number");
+      errorMessage += "age is not a number\n"
       surveyIsValid = false;
     }
     if (gender === "DEFAULT" || gender === "") {
-      console.log("choose gender");
+      errorMessage += "choose gender\n"
       surveyIsValid = false;
     }
     if (education === "DEFAULT" || education === "") {
-      console.log("choose edu");
+      errorMessage += "choose edu\n"
       surveyIsValid = false;
     }
     if (skills === "DEFAULT" || skills === "") {
-      console.log("choose skills");
+      errorMessage += "choose skills\n"
       surveyIsValid = false;
     }
 
     if (surveyIsValid === true) {
       console.log(opts);
-    }
 
       authFetch("/umfrage", {
         method: "post",
         body: JSON.stringify(opts),
       });
+    }
+    else {
+      console.log(errorMessage);
+    }
   };
 
   const handleAgeChange = (e) => {