Si tengo un formulario con los campos nombre, correo, dni y comentario deseo agregar a mí base de datos

ript
function addUser() {
  var name = document.getElementById("name").value;
  var email = document.getElementById("email").value;
  var password = document.getElementById("password").value;
  var password2 = document.getElementById("password2").value;
  var user = {
    name: name,
    email: email,
    password: password,
    password2: password2
  };
  var user =