index.js

import './shim'
// TODO Remove when this will be fixed - https://github.com/kmagiera/react-native-gesture-handler/issues/320
import 'react-native-gesture-handler'

import { AppRegistry } from 'react-native'
import App from './src/App'
import { name } from './app.json'

global.XMLHttpRequest = global.originalXMLHttpRequest
  ? global.originalXMLHttpRequest
  : global.XMLHttpRequest
global.FormData = global.originalFormData ? global.originalFormData : global.FormData

fetch() // Ensure to get the lazy property

if (window.__FETCH_SUPPORT__) {
  // it's RNDebugger only to have
  window.__FETCH_SUPPORT__.blob = false
} else {
  /*
   * Set __FETCH_SUPPORT__ to false is just work for `fetch`.
   * If you're using another way you can just use the native Blob and remove the `else` statement
   */
  global.Blob = global.originalBlob ? global.originalBlob : global.Blob
  global.FileReader = global.originalFileReader ? global.originalFileReader : global.FileReader
}
AppRegistry.registerComponent(name, () => App)