finished final project

catalog/js/login.js

@@ -0,0 +1,29 @@
+const form = document.querySelector("form");
+const username_field = document.querySelector("#username");
+const password_field = document.querySelector("#password");
+const submit_button = document.querySelector('input[type="submit"]');
+
+const err = document.querySelector("#invalid");
+
+submit_button.addEventListener("click", (e) => {
+  e.preventDefault();
+
+  fetch("functions/user.php", {
+    method: "POST",
+    headers: {
+      "Content-Type": "application/x-www-form-urlencoded",
+    },
+    body:
+      "form_id=login&username=" +
+      username_field.value +
+      "&password=" +
+      password_field.value,
+  })
+    .then((response) => {
+      return response.text(); // Parse response body as JSON
+    })
+    .then((data) => {
+      if (data == "true") form.submit();
+      else err.innerText = "Username or Password are incorrect.";
+    });
+});