miscoded

The HTML input element already defines a type attribute so it was a matter of adding new values, and my experiments looked at doing so for number and date. This worked fine on most browsers, but the Opera browsers handling of the type and required attributes made it necessary to support datatype and needed as alternatives.

(source)
Well, that's the sort of problem you get when re-inventing wheels: you have to figure out how to fit them in next to the wheels already in place. Meet the JavaScript car mechanic:

  // partial work around Opera's WF2 implementation for type
  // same technique doesn't work for required attribute :-(

Doesn't work for "required"? Seems like the JavaScript mechanic left his "removeAttribute" tool at home.

  if (nativewf2)
  {
    fields = document.getElementsByTagName("input");

    for (i = 0; i < fields.length; ++i)
    {
      field = fields[i];
      type = field.getAttribute("type");

      if (type == "number" || type == "date")
      {
        field.setAttribute("datatype", type);
        field.setAttribute("type", "text");

Look at those final setAttribute statements: since Opera's WF2 wheels apparently aren't good enough they are dismounted and the fancy JavaScript-required-XForms-Lite-wheels fitted instead. Why can't the mechanic simply say "OK, this car already has wheels so I don't need to do any work here"?

Are the differences between XForms Lite "date" and WF2 "date" so severe?

Why would one "required" be better than the other (besides from "required" being invented there while "required" isn't, that is..)?