Oops! There was an unhandled error: TypeError - Unable to retrieve property 'data' as it is undefined

I'm encountering an issue while working on my vue.js project.

Uncaught (in promise) TypeError: Cannot read property 'data' of undefined

Let's take a look at the code snippet where the error is happening.

In this piece of code, I am passing form data to the User class:

Login.vue

<script>
 export default {
     data(){
         return {
             form :{
                 email:null,
                 password:null
             }
         }
    },
    methods:{
        login(){
            User.login(this.form)
        }
    }
}
</script>

And here is the User class being used:

User.js

class User {
  login(data){
      axios.post('/api/auth/login',data)
          .then(res => this.responseAfterLogin(res))
          .catch(error => console.log(error.response.data))
  }
}
export default User = new User();

Interestingly, the error disappeared when I directly called the login method within Login.vue without involving the User class:

Login.vue

 <script>
 export default {
     data(){
         return {
             form :{
                 email:null,
                 password:null
             }
         }
    },
    methods:{
        login(){
            axios.post('/api/auth/login',this.form)
            .then(res => console.log(res.data))
            .catch(error => console.log(error.response.data))
        }
    }
}
 </script>

Can someone explain why this difference in behavior is happening and how can I properly pass data to the User class?

Answer №1

It is important to log either the response or error from your API in order to understand the data structure being returned.

axios.post('/api/auth/login', this.form)
.then(res => console.log(res, 'success'))
.catch(error => console.log(error, 'error'))

Answer №2

class LoginUser {
    authenticate(data) {
        axios.post('/api/auth/login', data)
            .then(function(response) {
                console.log(response.data)
            })

        .catch(function(errors) {
            console.log(errors.response.data);
        })
    }
}
export default AuthUser = new LoginUser()

authenticate() {
         AuthUser.authenticate(this.formData)
}

Answer №3

It's possible that your api is returning a null value, which could be due to an incorrect password/username combination, similar to what I experienced.

To address this issue, I implemented validation using a conditional statement to check for the null value and redirect if necessary. The code snippet looks like this:

console.log(data);
if (data == null) {
  console.log("Oops! Something went wrong.");
  window.location.href = '/'
}

The line of code:

window.location.href = '/'

Could be substituted with a different type of action.

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