Button does not submit form

Sometimes pressing a button does not result in submitting the form and calling JavaScript handlers of the submit event of the form.

Possible reasons:

• the button has button instead of submit as its type (the value of the type attribute);
• the button is outside of the form;
• the form is invalid, but this is unnoticeable:
  • the invalid form element is hidden,
  • or default styling (the outline or box-shadow property) for invalid elements (the :invalid pseudo­class) is reset;
• there was a JavaScript error either before submitting the form or in a handler of the submit event.