created web files

static/poster.js

@@ -0,0 +1,21 @@
+const submit_btn = document.getElementById('submit');
+const title_obj = document.getElementById('title');
+const desc_obj = document.getElementById('desc');
+const date_obj = document.getElementById('date');
+const messenger = document.getElementById('messenger');
+
+document.addEventListener('DOMContentLoaded')
+
+submit_btn.addEventListener(onclick, () => {
+    var title = title_obj.value;
+    var desc = desc_obj.value;
+    var date_str = date_obj.value;
+
+    if (title == null || desc == null || date == null) {
+        messenger.innerHTML = '請填寫所有欄位';
+        messenger.classList.remove("hide");
+        return;
+    }
+
+    const date = new Date(date_str);
+});