function vprintf (format, args) {
  // http://kevin.vanzonneveld.net
  // +   original by: Ash Searle (http://hexmen.com/blog/)
  // +   improved by: Michael White (http://getsprink.com)
  // + reimplemented by: Brett Zamir (http://brett-zamir.me)
  // -    depends on: sprintf
  // *     example 1: printf("%01.2f", 123.1);
  // *     returns 1: 6
  var body, elmt;
  var ret = '',
    d = this.window.document;

  // .shift() does not work to get first item in bodies
  var HTMLNS = 'http://www.w3.org/1999/xhtml';
  body = d.getElementsByTagNameNS ? (d.getElementsByTagNameNS(HTMLNS, 'body')[0] ? d.getElementsByTagNameNS(HTMLNS, 'body')[0] : d.documentElement.lastChild) : d.getElementsByTagName('body')[0];

  if (!body) {
    return false;
  }

  ret = this.sprintf.apply(this, [format].concat(args));

  elmt = d.createTextNode(ret);
  body.appendChild(elmt);

  return ret.length;
}

printf("%01.2f", 123.1);

6