Angular Form Validator: Password Strength with upper, lower and number

form.component.html

<form [formGroup]="form">
    <input type="password"
        formControlName="password">
    <p class="help is-danger"
        *ngIf="form.get('password').hasError('strong')">
        Must have at least one number, one lowercase and one uppercase letter.</p>
</form>

form.component.ts

import { Component } from '@angular/core';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
import { PasswordValidator } from 'password.validator';

@Component({
    selector: 'form',
    templateUrl: './form.component.html',
    styleUrls: ['./form.component.scss']
})
export class Form {
   
    form: FormGroup;
    
    constructor(private fb: FormBuilder) { 
        this.form = this.fb.group({
            password: ['', [PasswordValidator.strong]
            ],
        });     
    }  
}

password.validator.ts

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

export interface ValidationResult {
    [key: string]: boolean;
}

export class PasswordValidator {

    public static strong(control: FormControl): ValidationResult {
        let hasNumber = /\d/.test(control.value);
        let hasUpper = /[A-Z]/.test(control.value);
        let hasLower = /[a-z]/.test(control.value);
        // console.log('Num, Upp, Low', hasNumber, hasUpper, hasLower);
        const valid = hasNumber && hasUpper && hasLower;
        if (!valid) {
            // return what´s not valid
            return { strong: true };
        }
        return null;
    }
}