the document type declaration.
- Document Object Model (DOM) Level 1 Specification, Section 1.2
For HTML documents, the doctype property returns null, as defined by the World Wide Web Consortium (W3C) Document Object Model (DOM) Level 1 standard.
Windows Internet Explorer 9. The methods and properties of doctype object are supported only for webpages that are displayed in IE9 Standards mode. In other document compatibility modes and earlier versions of Windows Internet Explorer, the doctype object is null for HTML documents.
doctype was introduced in Microsoft Internet Explorer 6.