Comment by c-smile

Also, if to allow form.value to accept JSON-ish objects it will be possible to set form values in single shot:

   form.value = { transAmount: 12345n, transDate: new Date() };

where form is

   <form>
     ... <output type="currency" name="transAmount" />
     ... <output type="date-local" name="transDate" />
   </form>