index.js

// index.js
import { render } from "react-dom";
import { ApolloProvider } from "react-apollo";

import { App } from "./App";
import { createClient } from "./graphql";

const $app = document.getElementById("app");

const client = createClient({
  endpointUri: "https://api.graph.cool/...",
  onError: error => render(
    <MyErrorHandler error={error} />
  , $app)
});

render(
  <ApolloProvider client={client}>
    <App />
  </ApolloProvider>
, $app);