want to ask for symfony2 form text type, I have two fields to fill in: one is username, the other is email. Code something like:
$builder->add('username', TextType::class)
->add('email', TextType::class);
To save effort, I want when the user fills in username, the email will automatically be username@qq.com by default. But the user still can modify email if he wants. How to achieve that in symfony form type? How to modify the FormType class and need to use javascript in html? Thanks!