Fixing array and erros throws

Author: huv1k

README.md

@@ -74,7 +74,7 @@ The `props` argument accepts the following fields:
 
 | Key | Type | Default | Note |
 | ---  | --- | --- | --- |
-| `typeDefs` | String  |  `null` | Contains GraphQL type definitions in [SDL](https://blog.graph.cool/graphql-sdl-schema-definition-language-6755bcb9ce51) or file path to type definitions (required if `schema` is not provided \*)  |
+| `typeDefs` | `String` or `Function` or `DocumentNode` or `array` of previous |  `null` | Contains GraphQL type definitions in [SDL](https://blog.graph.cool/graphql-sdl-schema-definition-language-6755bcb9ce51) or file path to type definitions (required if `schema` is not provided \*)  |
 | `resolvers`  | Object  |  `null`  | Contains resolvers for the fields specified in `typeDefs` (required if `schema` is not provided \*) |
 | `schema`  | Object |  `null`  | An instance of [`GraphQLSchema`](http://graphql.org/graphql-js/type/#graphqlschema) (required if `typeDefs` and `resolvers` are not provided \*) |
 | `context`  | Object or Function  |  `{}`  | Contains custom data being passed through your resolver chain. This can be passed in as an object, or as a Function with the signature `(req: ContextParameters) => any` \*\* |

src/index.ts

@@ -304,7 +304,11 @@ function mergeTypeDefs(typeDefs: ITypeDefinitions): string {
     return print(typeDefs)
   }
 
-  return typeDefs.reduce<string>((acc, t) => acc + '\n' + mergeTypeDefs(t), '')
+  if (Array.isArray(typeDefs)) {
+    return typeDefs.reduce<string>((acc, t) => acc + '\n' + mergeTypeDefs(t), '')
+  }
+
+  throw new Error('Typedef is not string, function, DocumentNode or array of previous')
 }
 
 function isDocumentNode(node: any): node is DocumentNode {