Angular makes http request Twice

I have a mean stack going. Angular 5.

I'm grabbing data from a form and i'm calling a Service to handle sending the form-data to the backend api.

The service makes use of the HttpClient. It sends off a post request with the correct headers and payload. It successfully posts to the database

BUT... when i look in my console's Network tab, i see 2 identical requests being made! One succeeds because it's the intended request, but the other fails (which is supposed to fail because of duplicate data in db)

I don't understand why 2 requests are being made. I am using the mean stack so (i believe) there shouldn't be any CORS issues.

any ideas?

*UPDATED INFORMATION i checked the Networks tab

• 1st request has Request Method: POST (200 OK)
• 2nd request also has Request Method: POST (500)
• in console tab, 2nd request error coming from zone.js (webpack?)

my form

<form [formGroup]="registerForm" (ngSubmit)="onSubmit()">
  <div class="form-group">
    <label for="username">Username</label>
    <input 
      type="text" 
      id="username"
      class="form-control"
      formControlName="username"
      placeholder="username" >
  </div>
  <div class="form-group">
    <label for="email">Email</label>
    <input 
      type="email" 
      id="email"
      class="form-control"
      formControlName="email"
      placeholder="email" >
  </div>
  <div class="form-group">
    <label for="password">Password</label>
    <input 
      type="password" 
      id="password"
      class="form-control"
      formControlName="password"
      placeholder="password" >
  </div>
  <div class="form-group">
    <label for="name">Restaurant Name</label>
    <input 
      type="text" 
      id="name"
      class="form-control"
      formControlName="name"
      placeholder="Restaurant Name" >
  </div>    
  <div class="form-group">
    <label for="url">Restaurant Url <br> <small class="form-text text-
    muted">A link that will take patrons to your list of available food 
    items</small></label>
    <input 
          type="text" 
          id="url"
          class="form-control form-contol-sm"
          formControlName="url"
          placeholder="RosasPizza123" >

  </div>
  <div class="form-group">
    <label for="address">Address</label>
    <input 
      type="text" 
      id="address"
      class="form-control"
      formControlName="address"
      placeholder="125 Address st" >
  </div>
  <div class="form-group">
    <label for="city">City/Town</label>
    <input 
      type="text" 
      id="city"
      class="form-control"
      formControlName="city"
      placeholder="Newburgh" >
  </div>
  <div class="form-group">
    <label for="state">State</label>
    <input 
      type="text" 
      id="state"
      class="form-control"
      formControlName="state"
      placeholder="NY"
      maxlength="2" >
  </div>
  <div class="form-group">
    <label for="zipcode">Zipcode</label>
    <input 
      type="text" 
      id="zipcode"
      class="form-control"
      formControlName="zipcode"
      placeholder="zipcode" >
  </div>
  <div class="form-group">
    <label for="phone">Phone</label>
    <input 
        type="tel" 
        id="phone"
        class="form-control"
        formControlName="phone"
        placeholder="phone" >
    </div>
    <button (click)="onSubmit()">Register</button>  
</form>

in .ts file

export class RegisterComponent implements OnInit {
  registerForm: FormGroup;

  constructor( private userService: UserService) { }

  ngOnInit() {    
    this.registerForm = new FormGroup({
      'username': new FormControl(null, Validators.required),
      'email': new FormControl(null, [
              Validators.required,
              Validators.email]),
      'password': new FormControl(null, Validators.required),
      'name': new FormControl(null, Validators.required),
      'url': new FormControl(null, Validators.required),
      'address': new FormControl(null, Validators.required),
      'city': new FormControl(null, Validators.required),
      'state': new FormControl(null, [
              Validators.required,
              Validators.maxLength(2)]),
      'zipcode': new FormControl(null, Validators.required),
      'phone': new FormControl(null),
   });
  }

onSubmit() {        
  const newUser = new User(
    this.registerForm.value.username,
    this.registerForm.value.email,
    this.registerForm.value.password,
    this.registerForm.value.name,
    this.registerForm.value.url,
    this.registerForm.value.address,
    this.registerForm.value.city,
    this.registerForm.value.state,
    this.registerForm.value.zipcode,
    this.registerForm.value.phone
  );

this.userService.register(newUser)
    .subscribe(
      (response) => {

        console.log("response", response);
      },
      () => {}
    );
  }

}

in service file

   @Injectable()
   export class UserService {
     url = 'http://localhost:3000/api/';

     constructor(private http: HttpClient) {}

    // register user
     register(user: User) {
        const userString = JSON.stringify(user);
        const httpOptions = {
            headers: new HttpHeaders({
                'Content-Type': 'application/json'
                // auth: 'my-token'
            })
        };
        return this.http.post(this.url + 'register', userString, httpOptions);       
     }

    }