根据angular form构建器/组中其他字段的值，对一个字段运行并设置验证错误

import { FormGroup, Validators } from '@angular/forms';

myForm: FormGroup;

constructor() {
  this.myForm = new FormGroup({
    field1: ['', Validators.required],
    field2: ['', Validators.required],
    field3: ['', Validators.required]
  });
}

<form [formGroup]="myForm">
  <input type="text" formControlName="field1">
  <input type="text" formControlName="field2">
  <input type="text" formControlName="field3">
</form>

ngOnInit() {
  this.myForm.get('field1').valueChanges.subscribe(value => {
    const field2Value = this.myForm.get('field2').value;
    const field3Value = this.myForm.get('field3').value;

    if (value === field2Value && value === field3Value) {
      this.myForm.get('field1').setErrors({ customError: true });
    } else {
      this.myForm.get('field1').setErrors(null);
    }
  });
}

<div *ngIf="myForm.get('field1').errors?.customError">
  Field 1 value should be different from Field 2 and Field 3.
</div>