Native Facebook login with React Native from http://brentvatne.ca/facebook-login-with-react-native/

FacebookLoginManager.m

#import "FacebookLoginManager.h"
#import "FBSDKCoreKit/FBSDKCoreKit.h"
#import "FBSDKLoginKit/FBSDKLoginKit.h"

@implementation FacebookLoginManager

- (void)newSession:(RCTResponseSenderBlock)callback {
    RCT_EXPORT();

    FBSDKLoginManager *login = [[FBSDKLoginManager alloc] init];
    [login logInWithReadPermissions:@[@"public_profile", @"email"] handler:^(FBSDKLoginManagerLoginResult *result, NSError *error) {
        
        if (error) {
            callback(@[@"Error", [NSNull null]]);
        } else if (result.isCancelled) {
            callback(@[@"Canceled", [NSNull null]]);
        } else {
            FBSDKAccessToken *token = result.token;
            NSString *tokenString = token.tokenString;
            NSString *userId = token.userID;
            NSDictionary *credentials = @{ @"token" : tokenString, @"userId" : userId };
            callback(@[[NSNull null], credentials]);
        }
    }];
}

@end

index.ios.js

var React = require('react-native');
var {
  AppRegistry,
  StyleSheet,
  Text,
  View,
  TouchableHighlight
} = React;

var FacebookLoginManager = require('NativeModules').FacebookLoginManager;

var FacebookLogin = React.createClass({
  getInitialState() {
    return {
      result: '...'
    }
  },

  componentDidMount() {
    var self = this;
  },

  login() {
    FacebookLoginManager.newSession((error, info) => {
      if (error) {
        this.setState({result: error});
      } else {
        this.setState({result: info});
      }
    });
  },

  render() {
    return (
      <View style={styles.container}>
        <TouchableHighlight onPress={this.login}>
          <Text style={styles.welcome}>
            Facebook Login
          </Text>
        </TouchableHighlight>
        <Text style={styles.instructions}>
          {this.state.result}
        </Text>
      </View>
    );
  }
});