Abstract JS for multivalue form fields

bookwyrm/static/js/bookwyrm.js

@@ -368,4 +368,22 @@ let BookWyrm = new class {
             );
         }
     }
+
+    duplicateInput (input_id ) {
+        const orig = document.getElementById(input_id);
+        const parent = orig.parentNode;
+        const new_count = parent.querySelectorAll("input").length + 1
+
+        let input = orig.cloneNode();
+
+        input.id += ("-" + (new_count))
+        input.value = ""
+
+        let label = parent.querySelector("label").cloneNode();
+
+        label.setAttribute("for", input.id)
+
+        parent.appendChild(label)
+        parent.appendChild(input)
+    }
 }();