Check for FormData before checking for object when preparing body (#249)

* Check for FormData before checking for object when preparing body

* Add todo

* Cleanup

Author: sbichenko

README.md

@@ -1097,6 +1097,8 @@ Todos
 
 - [ ] make code editor plugin/package/extension that adds GraphQL syntax highlighting for `useQuery` and `useMutation` 😊
 
+- [ ] add React Native test suite
+
 [1]: https://github.com/ava/use-http/issues/new?title=[Feature%20Request]%20YOUR_FEATURE_NAME
 [2]: https://github.com/ava/use-http/issues/93#issuecomment-600896722
 [3]: https://github.com/ava/use-http/raw/master/public/dog.png

src/doFetchArgs.ts

@@ -37,8 +37,10 @@ export default async function doFetchArgs<TData = any>(
   const url = `${initialURL}${path}${route}`
 
   const body = ((): BodyInit | null => {
-    if (isBodyObject(routeOrBody)) return JSON.stringify(routeOrBody)
+    // FormData instanceof check should go first, because React Native's FormData implementation
+    // is indistinguishable from plain object when using isBodyObject check
     if (routeOrBody instanceof FormData) return routeOrBody
+    if (isBodyObject(routeOrBody)) return JSON.stringify(routeOrBody)
     if (
       !isServer &&
       ((bodyAs2ndParam as any) instanceof FormData ||