Lib: Add form helpers

src/lib/forms.ts

@@ -0,0 +1,48 @@
+import { error } from "@sveltejs/kit";
+
+/**
+ * Obtain the value of the key "id" and remove it from the FormData.
+ * Throws SvelteKit error(400) if "id" is not found.
+ */
+export const form_data_get_and_remove_id = (data: FormData): string => {
+  const id: string | undefined = data.get("id")?.toString();
+  if (!id) error(400, "Missing ID");
+  data.delete("id");
+  return id;
+};
+
+/**
+ * Remove empty fields and files from FormData objects.
+ */
+export const form_data_clean = (data: FormData): FormData => {
+  for (const [key, value] of data.entries()) {
+    if (value === "") {
+      // Remove empty keys
+      data.delete(key);
+    } else if (
+      // Remove empty files
+      typeof value === "object" &&
+      value !== null &&
+      "size" in value &&
+      value.size === 0
+    ) {
+      data.delete(key);
+    }
+  }
+
+  return data;
+};
+
+/**
+ * Throws SvelteKit error(400) if form_data does not contain key.
+ */
+export const form_data_ensure_key = (data: FormData, key: string) => {
+  if (!data.get(key)) error(400, `Key "${key}" missing from form_data!`);
+};
+
+/**
+ * Throws SvelteKit error(400) if form_data does not contain all keys.
+ */
+export const form_data_ensure_keys = (data: FormData, keys: string[]) => {
+  keys.map((key) => form_data_ensure_key(data, key));
+};

src/lib/index.ts

@@ -1 +0,0 @@
-// place files you want to import through the `$lib` alias in this folder.