refactor: minor JS refactor

www/js/loginform.js

 // Helper functions
+function getElement(id) {
+  return document.getElementById(id);
+}
+
 function value(id) {
-  const element = document.getElementById(id);
-  if (element != null) {
-    return element.value;
-  } else {
-    console.log(id + " is null!");
-  }
-  return "";
+  const element = getElement(id);
+  return element === null ? "" : element.value;
+}
+
+function getContent(id) {
+  const element = getElement(id);
+  return element === null ? "" : element.content;
 }
 
 function booleanValue(id) {
@@ -14,45 +18,37 @@ function booleanValue(id) {
 }
 
 function set(id, value) {
-  const element = document.getElementById(id);
+  const element = getElement(id);
   if (element != null) {
     element.value = value;
-  } else {
-    console.log(id + " is null!");
   }
 }
 
 function disable(id) {
-  const element = document.getElementById(id);
+  const element = getElement(id);
   if (element != null) {
     element.classList.add("hidden");
-  } else {
-    console.log(id + " is null!");
   }
 }
 
 function enable(id) {
-  const element = document.getElementById(id);
+  const element = getElement(id);
   if (element != null) {
     element.classList.remove("hidden");
-  } else {
-    console.log(id + " is null!");
   }
 }
 
 function changeMode(newMode) {
-  document.getElementById("mode").value = newMode;
-  document.getElementById("modeChanged").value = "true";
+  set("mode", newMode);
+  set("modeChanged", "true");
   document.forms["piLoginForm"].submit();
 }
 
 function t(key) {
-  return JSON.parse(
-    document.getElementById("privacyidea-translations").content
-  )[key];
+  return JSON.parse(getContent("privacyidea-translations"))[key];
 }
 
-const step = document.getElementById("privacyidea-step").content;
+const step = getContent("privacyidea-step");
 
 if (step > "1") {
   disable("username");
@@ -225,23 +221,17 @@ function sign_u2f_request(signRequest) {
   });
 }
 
-if (document.getElementById("privacyidea-hide-alternate").content === "true") {
-  document.getElementById("AlternateLoginOptions").classList.add("hidden");
+if (getContent("privacyidea-hide-alternate") === "true") {
+  disable("AlternateLoginOptions");
 }
 
 document.addEventListener("DOMContentLoaded", (event) => {
-  document
-    .getElementById("useWebAuthnButton")
-    .addEventListener("click", doWebAuthn);
-  document
-    .getElementById("usePushButton")
-    .addEventListener("click", function () {
-      changeMode("push");
-    });
-  document
-    .getElementById("useOTPButton")
-    .addEventListener("click", function () {
-      changeMode("otp");
-    });
-  document.getElementById("useU2FButton").addEventListener("click", doU2F);
+  getElement("useWebAuthnButton").addEventListener("click", doWebAuthn);
+  getElement("usePushButton").addEventListener("click", function () {
+    changeMode("push");
+  });
+  getElement("useOTPButton").addEventListener("click", function () {
+    changeMode("otp");
+  });
+  getElement("useU2FButton").addEventListener("click", doU2F);
 });