const formById = document.getElementById('login');
const formByName = document.getElementsByName('login')[0];
const formBySelector = document.querySelector('form');
const formByFormsField = document.forms[0];
const formByNameField = document.login;

console.log(formById.id);
console.log(formByName.id);
console.log(formBySelector.id);
console.log(formByFormsField.id);
console.log(formByNameField.id);