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validateForm!: FormGroup;

 submitForm(): void {
  for (const i in this.validateForm.controls) {
   this.validateForm.controls[i].markAsDirty();
   this.validateForm.controls[i].updateValueAndValidity();
  }
 }

 constructor(private fb: FormBuilder) {}

 ngOnInit(): void {
  this.validateForm = this.fb.group({
   userName: [null, [Validators.required]],
   password: [null, [Validators.required]],
   remember: [true]
  });
 }

export class SimpleFormComponent implements OnInit {
 validateForm: FormGroup;
 errMessageMap = {};

 constructor(
  private fb: FormBuilder
 ) { }

 ngOnInit() {
  this.errMessageMap = {
   userName: {
    required: 'please input your name!',
    minlength: 'please input at least least 5 character'
   },
   password: {
    required: 'please input your password!'
   }
  };
  this.validateForm = this.fb.group({
   userName: [null, [Validators.required, Validators.minLength(5)]],
   password: [null, [Validators.required]],
   remember: [true]
  }, { updateOn: 'change' });
 }
 submitForm(): void {
  if (this.validateForm.controls) {
   for (const i in this.validateForm.controls) {
    if (this.validateForm.controls[i]) {
     this.validateForm.controls[i].markAsDirty();
     this.validateForm.controls[i].updateValueAndValidity();
    }
   }
  }
 }
 getErrTipByField(fieldName) {
  const errors = this.validateForm.get(fieldName).errors;
  let errMsg = '';
  for (const key in errors) {
   if (errors.hasOwnProperty(key)) {
    errMsg += this.errMessageMap[fieldName][key];
   }
  }
  return errMsg;
 }

}