const USER_1 = {
  name: 'Tom',
  age: 20,
  traits: {
    hair: 'black',
    eyes: 'blue'
  }
}

const USER_2 = {
  name: 'Sarah',
  age: 21,
  hobby: 'cars',
  traits: {
    eyes: 'green',
  }
}


mergeUsers = async () => {
  try {
    //save first user
    await AsyncStorage.setItem('@MyApp_user', JSON.stringify(USER_1))

    // merge USER_2 into saved USER_1
    await AsyncStorage.mergeItem('@MyApp_user', JSON.stringify(USER_2))

    // read merged item
    const currentUser = await AsyncStorage.getItem('@MyApp_user')

    console.log(currentUser)

    // console.log result:
    // {
    //   name: 'Sarah',
    //   age: 21,
    //   hobby: 'cars',
    //   traits: {
    //     eyes: 'green',
    //     hair: 'black'
    //   }
    // }
  }
}