loan-amount-validator.ts

import { Injectable } from '@angular/core';
import { FormGroup, ValidationErrors, ValidatorFn } from '@angular/forms';

@Injectable({
  providedIn: 'root'
})
export class LoanAmountValidatorService {

  constructor() { }

  identityRevealedValidator: ValidatorFn = (formGroup: FormGroup): ValidationErrors | null => {
    const income = formGroup.get('income');
    const expenses = formGroup.get('expenses');

    return income && expenses && income.value - expenses.value > 100000 ? { 'loanAmount': true } : null;
  };
}