Implement attachment CollectionType using stimulus

assets/controllers/elements/attachmenttype_change_controller.js

@@ -0,0 +1,29 @@
+import {Controller} from "@hotwired/stimulus";
+
+/**
+ * This controller synchronizes the filetype filters of the file input type with our selected attachment type
+ */
+export default class extends Controller
+{
+    _selectInput;
+    _fileInput;
+
+    connect() {
+        //Find the select input for our attachment form
+        this._selectInput = this.element.querySelector('select');
+        //Find the file input for our attachment form
+        this._fileInput = this.element.querySelector('input[type="file"]');
+
+        this._selectInput.addEventListener('change', this.updateAllowedFiletypes.bind(this));
+
+        //Update file file on load
+        this.updateAllowedFiletypes();
+    }
+
+    updateAllowedFiletypes() {
+        let selected_option = this._selectInput.options[this._selectInput.selectedIndex];
+        let filetype_filter = selected_option.dataset.filetype_filter;
+        //Apply filetype filter to file input
+        this._fileInput.setAttribute('accept', filetype_filter);
+    }
+}