alert(document.doctype.name)
var isDoctype = function(el) { return /^(<!DOCTYPE|<\?xml)/i.test(el.text); }; var comments = targetDocument.getElementsByTagName('!'); for (var i = 0; isDoctype(comments[i]); i++) { doctype += comments[i].text; }
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title></title> </head> <body> <script type="text/javascript"> var Doctype =/CSS/.test(document.compatMode)&&document.getElementsByTagName('!')[0].data; document.write(Doctype) </script> </body> </html>