Improve errors on signup form validation

src/script.js

@@ -19,17 +19,27 @@ let resetMessage = () => {
   document.getElementById("empty-error-message").hidden = true;
 };
 
+let isNewEmail = (email) => {
+  return usersTable.filter((user) => user.username === email).length === 0;
+};
+
+let isEmptyEmail = (email) => {
+  return email.length === 0;
+};
+
 addEventListener("submit", (event) => {
   event.preventDefault();
   resetMessage();
 
   let email = document.getElementById("email").value;
 
-  // TODO: Show Correct Status Messages on Signup Form
-  // 1. successful signup
-  // 2. empty email
-  // 3. taken email
-  // 4. repeat email
+  if (isEmptyEmail(email)) {
+    renderEmailEmptyError();
+  } else if (isNewEmail(email)) {
+    renderSuccess();
+  } else {
+    renderEmailTakenError();
+  }
 });
 
 let toggleNav = () => {