可能未处理的promise promise（id：2）：ReferenceError：找不到变量：responseJson

I have a app which have PHP back-end and it was well functioned and it sent and received data from MySQL database.Suddenly I got this warning and it is not sending the data in register form to the DB either it does not perform login. Need help for this.

Possibble unhandled promise reaction(id:2): ReferenceError:Can't find variable: responseJson

Below the code used for registration.

 fetch('http://localhost/test/register.php', {
  method: 'POST',
  headers: {
    'Accept': 'application/json',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    email: email,
    password: password,
    date: date,
    date2: date2,
    name: name,
    number: number,
    text: text,
    text1: text1
  })

}).then((response) => response.json())
  .then((responseJson) => {
    Alert.alert(responseJson);
  }).catch((error) => {
    Alert.alert(responseJson);
  });

}