When a buyer goes through the checkout process as anonymous guest, he specifies his email at the "Order information" step in the input
<input data-drupal-selector="edit-contact-information-email" type="email" id="edit-contact-information-email" name="contact_information[email]" value="" size="60" maxlength="254" class="form-email required" required="required" aria-required="true">
The email is stored in the column mail of the table commerce_order of the database.
I would like to store a text string via this input in the database.
If I fill the input by JS with text string and even change the type attribute of the input from email to text, the data is not stored in the DB. So there is email validating somewhere.
Where is the validating in JS or PHP?
Or how can I resolve the issue?
You should check the hook form_alter.
Also, you should take a look into the drupal checkout docs too:
https://docs.drupalcommerce.org/commerce2/user-guide/checkout/configure-checkout
You should be aware that changing a form type may impact all other places that needs to read this data.
Regarding the hook alter, Here goes an example.
function mymodule_form_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {
if ($form_id == 'myformID') {
$form['myformMachineName']['myfield']['#type'] = 'textfield';
}
}