Json response reactnative fetch login data

Question

Im trying to fetch my login data using the login fetch method below which raises an error. I'm not sure why it raises this error and where its going wrong.

i get this error

[Unhandled promise rejection: TypeError: undefined is not an object (evaluating 'res._bodyText')]

login fetch method

createUser: (username, password) => {
    return (
      fetch('http://192.168.0.140:80/auth/login/', {
        method: 'POST',
        dataType: 'jsonp',
        credentials: 'omit',
        headers: {
          'Content-Type': 'application/json',
          'Accept': 'application/json'
        },
        body: JSON.stringify({
          username: username,
          password: password
        })
      })


    )
  },

in my login.js

state = {
    username: '',
    password: ''
  }

login = () => {
    if (this.state.username === '') {
      alert('Enter username !')
    } else if (this.state.password === '') {
      alert('Enter Password !')
    } else {
      api
        .createUser(this.state.username, this.state.password)
        .then((response) => response.json())
        //If response is in json then in success
        .then((responseJson) => {
          //Success
          console.log(responseJson)
        })
        //If response is not in json then in error
        .catch((error) => {
          //Error
          console.error(error)
          alert(error)
        })
    }
  }

calling the login()

<TouchableNativeFeedback onPress={() => this.login()}>
                    <View style={styles.buttonContainer}>
                      <Text bold style={styles.buttonText}>
                        Login
                      </Text>
                    </View>
                  </TouchableNativeFeedback>

Answer 1

this could help you:

import {Alert} from 'react-native'

login = () => {
    if (this.state.username === '') {
      Alert.alert('Enter username !')
    } else if (this.state.password === '') {
      Alert.alert('Enter Password !')
    } else {
      api
        .createUser(this.state.username, this.state.password)
        .then((response) => {
            if(response.ok) {
              Alert.alert('Login successful')
            }else{
              Alert.alert('Check credentials')
            }
        })
        //If response is in json then in success
        
        //If response is not in json then in error
        .catch((error) => {
          //Error
          Alert.alert('Check credentials')
        })
    }
  }