Is the JS code written correctly?

Question

JavaScript

Greetings comrades, I'm learning how to create websites, and the following problem arose, I'm making a submission form, and validation by e-mail does not work, tell me what could be the problem?

"use strict"

document.addEventListener('DOMContentLoader', function () {
    const form = document.getElementById('form');
    form.addEventListener('submit', formSend);

    async function formSend(e) {
        e.preventDefault();

        let error = formValidate(form);

    }


    function formValidate(form) {
        let error = 0;
        let formReq = document.querySelectorAll('._req');

        for (let index = 0; index < formReq.length; index++) {
            const input = formReq[index];
            formRemoveError(input);

            if(input.classList.contains('_email')){
                if (emailTest(input)) {
                    formAddError(input);
                    error++;
                }
            } else if (input.getAttribute('type') === 'checkbox' && input.checkbox === false) {
                formAddError(input)
                error++;
            } else {
                if (input.value === '') {
                    formAddError(input);
                    error++;
                }
            }

        }
    }

    function formAddError(input) {
        input.parentElement.classList.add('_error');
        input.classList.add('_error');
    }

    function formRemoveError(input) {
        input.parentElement.classList.remove('_error');
        input.classList.remove('_error');
    }

    //Функция проверки E-mail
    function emailTest(input) {
        return /^(([^<>()[\]\\.,;:\[email protected]"]+(\.[^<>()[\]\\.,;:\[email protected]"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/.test(input.value);
    }
});