Validação de CPF usando angular - CpfValidator.numberValidator() no seu campo do form group

cpf-validator.ts

import {AbstractControl} from '@angular/forms';

export const CpfValidator = {
    numberValidator:function(){
        return (control:AbstractControl):{[key:string]:any} =>{
            let  multipliers = [10,9,8,7,6,5,4,3,2]
            let value = control.value.replace(/\D+/g, '');
            if(value.length===11){
                control.markAsTouched();
                let total = value.split('').reduce((total, item) => {
                    return total+=parseFloat(item)
                },0.0);
                total/=11;
                if(total==value[0]){
                    return {cpfRule:{value:control.value, message:'CPF inválido'}};
                }
                let digit = value.substr(value.length-2,value.length);
                let cpf = value.substr(0,value.length-2);
                total = multipliers.reduce((total, multipler, index) => {
                    return total + (cpf[index] * multipler);
                }, 0);
                let firstDigit = total%11;
                if(firstDigit<2){
                    firstDigit = 0;
                }else{
                    firstDigit = 11 - firstDigit;
                }
                cpf+=firstDigit;
                multipliers.unshift(11);
                total = multipliers.reduce((total, multipler, index) => {
                    return total + (cpf[index] * multipler);
                }, 0);
                let secondDigit = (total%11);
                if(secondDigit<2){
                    secondDigit = 0;
                }else{
                    secondDigit = 11 - secondDigit;
                }
                let calculatedDigit = `${firstDigit}${secondDigit}`;
                if(calculatedDigit===digit){
                    return null;
                }else{
                    return {cpfRule:{value:control.value, message:'CPF inválido'}};        
                }
            }else{
                return {minLength:{requiredLength:11,actualLength:value.length,message:`O tamanho mínimo é de 11 caracteres`}}
            }  
        }
    }
}