[angular] How to dynamically add and remove form fields in Angular 2

add and remove text input element dynamically any one can use this this will work Type of Contact Balance Fund Equity Fund Allocation Allocation % is required! Remove Add Contact

userForm: FormGroup;
  public contactList: FormArray;
  // returns all form groups under contacts
  get contactFormGroup() {
    return this.userForm.get('funds') as FormArray;
  }
  ngOnInit() {
    this.submitUser();
  }
  constructor(public fb: FormBuilder,private router: Router,private ngZone: NgZone,private userApi: ApiService) { }
  // contact formgroup
  createContact(): FormGroup {
    return this.fb.group({
      fundName: ['', Validators.compose([Validators.required])], // i.e Email, Phone
      allocation: [null, Validators.compose([Validators.required])]
    });
  }


  // triggered to change validation of value field type
  changedFieldType(index) {
    let validators = null;

    validators = Validators.compose([
      Validators.required,
      Validators.pattern(new RegExp('^\\+[0-9]?()[0-9](\\d[0-9]{9})$')) // pattern for validating international phone number
    ]);

    this.getContactsFormGroup(index).controls['allocation'].setValidators(
      validators
    );

    this.getContactsFormGroup(index).controls['allocation'].updateValueAndValidity();
  }

  // get the formgroup under contacts form array
  getContactsFormGroup(index): FormGroup {
    // this.contactList = this.form.get('contacts') as FormArray;
    const formGroup = this.contactList.controls[index] as FormGroup;
    return formGroup;
  }

  submitUser() {
    this.userForm = this.fb.group({
      first_name: ['', [Validators.required]],
      last_name: [''],
      email: ['', [Validators.required]],
      company_name: ['', [Validators.required]],
      license_start_date: ['', [Validators.required]],
      license_end_date: ['', [Validators.required]],
      gender: ['Male'],
      funds: this.fb.array([this.createContact()])
    })
    this.contactList = this.userForm.get('funds') as FormArray;
  }
  addContact() {
    this.contactList.push(this.createContact());
  }
  removeContact(index) {
    this.contactList.removeAt(index);
  }