diff --git a/ts/base/common.ts b/ts/base/common.ts
index f1dedb5..5036ec0 100644
--- a/ts/base/common.ts
+++ b/ts/base/common.ts
@@ -65,3 +65,22 @@ document.addEventListener("DOMContentLoaded", function () {
         });
     }
 });
+
+// * Input Validation.
+document.addEventListener("DOMContentLoaded", function () {
+    document.querySelectorAll("input.is-invalid").forEach((input) => {
+        let timer: NodeJS.Timeout|null = null;
+        input.addEventListener("input", () => {
+            if (timer) {
+                clearTimeout(timer);
+            }
+            timer = setTimeout(() => {
+                const parent = input.parentElement;
+                input.classList.remove("is-invalid");
+                if (parent && parent.classList.contains("is-invalid")) {
+                    parent.classList.remove("is-invalid");
+                }
+            }, 250);
+        });
+    });
+});