AppDelegate.m

#import "AppDelegate.h"

#import "RCTRootView.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
 
 //other code
  
  RCTRootView *rootView;
  if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad) }
    rootView = [[RCTRootView alloc] initWithBundleURL:jsCodeLocation
                                           moduleName:@"AppNameIpad"
                                        launchOptions:launchOptions]; 
  } else {
    rootView = [[RCTRootView alloc] initWithBundleURL:jsCodeLocation
                                           moduleName:@"AppNameIphone"
                                        launchOptions:launchOptions]; 
  }

  self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
  UIViewController *rootViewController = [[UIViewController alloc] init];
  rootViewController.view = rootView;
  self.window.rootViewController = rootViewController;
  [self.window makeKeyAndVisible];
  return YES;
}

@end

index.ios.js

//...
var AppNameIphone = React.createClass({
  //..
});

var AppNameIpad = React.createClass({
  //..
});

AppRegistry.registerComponent('AppNameIphone', () => AppNameIpone);
AppRegistry.registerComponent('AppNameIpad', () => AppNameIpad);