Angular 8 is throwing an error stating that the property 'token' is not recognized on the 'Object' data type

As a newcomer to Angular, I have been following the MEAN Stack - Mean Auth App Tutorial in Angular 2. However, since I am using Angular 8, some of the code is deprecated due to recent updates. I have encountered an issue with the code below and I'm unsure how to resolve it.

The code in my Auth.service.ts is functioning without errors:

    authenticateUser(user){
    let headers = new HttpHeaders();
    headers.append('Content-Type','application/json');
    return this.http.post('http://localhost:3000/users/authenticate', user,{headers: headers})
  }

  storeUserData(token, user){
    localStorage.setItem('id_token', token);
    localStorage.setItem('user', JSON.stringify(user));
    this.authToken = token;
    this.user = user;
  }

  logout(){
    this.authToken = null;
    this.user = null;
    localStorage.clear();
  }

In my login.component.ts, there's an error being displayed:

Property 'token' does not exist on type 'Object'

Property 'user' does not exist on type 'Object'

Property 'msg' does not exist on type 'Object'

This is the code from my login.component.ts:

onLoginSubmit(){
    const user = {
      username: this.username,
      password: this.password
    }

    this.authService.authenticateUser(user).subscribe(data => {
      if(data){
        this.authService.storeUserData(data.token, data.user);
        this.flashMessage.show('You are now logged in', {
          cssClass: 'alert-success',
          timeout: 5000});
        this.router.navigate(['dashboard']);
      } else {
        this.flashMessage.show(data.msg, {
          cssClass: 'alert-danger',
          timeout: 5000});
        this.router.navigate(['login']);
      }
    });
  }

In my login.components.ts file, when I input incorrect login credentials, it still logs me in, which should not happen.

 onLoginSubmit(){
    const user = {
      username: this.username,
      password: this.password
    }

    this.authService.authenticateUser(user).subscribe(data => {
      console.log(data);
      if(user){
        this.authService.storeUserData(data.token, data.user);
        this.flashMessage.show('You are now logged in', {
          cssClass: 'alert-success',
          timeout: 5000});
        this.router.navigate(['dashboard']);
      } else {
        this.flashMessage.show(data.msg, {
          cssClass: 'alert-danger',
          timeout: 5000});
        this.router.navigate(['login']);
      }
    });
  }

Answer №1

It appears that the TypeScript error you are encountering is related to the http.post method returning an Observable<object>. This means that the `data` being returned is an `object`, but it does not contain properties such as `token`, `user`, or `msg`.

Based on the information provided, your `authenticate` Web Service should ideally return:

interface SuccessResponse {
  token: string;
  user: any; // Ensure to replace 'any' with the appropriate type for a user
}

interface FailureResponse {
  success: false;
  msg: string;
}

type AuthResponse = SuccessResponse | FailureResponse;

authenticateUser(user): Observable<AuthResponse> {
    // The header for the content-type field is unnecessary
    return this.http.post<AuthResponse>('http://localhost:3000/users/authenticate', user);
}

You can implement it like this:

 onLoginSubmit() {
    const user = {
      username: this.username,
      password: this.password
    }

    this.authService.authenticateUser(user).subscribe(response => {
      console.log(data);
      if ('token' in response) {
        // Response corresponds to SuccessResponse
        this.authService.storeUserData(response.token, response.user);
        this.flashMessage.show('You are now logged in', {
          cssClass: 'alert-success',
          timeout: 5000});
        this.router.navigate(['dashboard']);
      } else {
        // Response corresponds to FailureResponse
        this.flashMessage.show(response.msg, {
          cssClass: 'alert-danger',
          timeout: 5000});
        this.router.navigate(['login']);
      }
    });
  }

This implementation should resolve your issue. However, it's important to note that when a login fails, the standard practice is to return an error (e.g., status code 401) instead of an OK status (200) with success: false. In that scenario, the code would need to be adjusted accordingly.

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