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doctype object

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Represents a Document Type Definition (DTD).

The DTD can be specified with the !DOCTYPE element in HTML and XML documents. With the doctype object, type declarations like entities, notations and the name of the DTD can be retrieved, furthermore the DTD can be specified for a XML documents (see the createDocumentType method).

Note: In Internet Explorer, the doctype object is not supported in HTML documents only in XML documents. The document.doctype property always returns null in that browser.

The following section describes the document type definition in HTML and XML.

!DOCTYPE element:

Each HTML and XML document can have only one !DOCTYPE element and it must be placed before the root element (the html element in HTML documents) of the document. The DTD specifies the syntax of the document and affects the visual appearance of the page.

<!DOCTYPE RootElement Availability "URI" [declarations]>

RootElement

Specifies the top-level element of the document

HTML

Normal HTML document.

Availability

Specifies whether the FPI (formal public identifier) is a system resource or open to the public.

PUBLIC	-	Open to the public.
SYSTEM	-	Private system resource.

URI

The URI of the DTD. For example, "-//W3C//DTD HTML 4.01//EN".

declarations

Specifies the location or the declaration of entities and elements used to parse the document.
For example, "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd".

Commonly used document types: Excluding special cases, the use of the XHTML 1.1 DTD doctype is recommended.

Document type	Declaration
XHTML 1.1 DTD:	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
XHTML 1.1 Strict DTD	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
XHTML 1.1 Transitional DTD	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
XHTML 1.1 Frameset DTD	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
XHTML 1.0 Strict	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
XHTML 1.0 Transitional	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
XHTML 1.0 Frameset	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
HTML 4.01 Strict	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
HTML 4.01 Transitional	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
HTML 4.01 Frameset	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">
HTML 3.2	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
HTML 2.0	<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">

Syntax:

Properties that reference the object:

•	object.doctype
	Related objects: document, XMLDocument

Methods that return the object:

•	implementation.createDocumentType (qualifiedName, publicID, systemID)

The base interface, through which you can add new functionalities to the doctype object, is the DocumentType interface.

If you want to see the HTML objects by categories, please visit this page.

HTML page for this element: !DOCTYPE

Possible members:

Properties

Methods

baseURI

Returns the base URL for the object.

entities

Returns a collection of available entity nodes in the document.

internalSubset

Returns the entire contents of the doctype element as a string.

name

Returns the name of the doctype element.

nextSibling

Returns a reference to the next child of the current element's parent.

nodeName

Returns the name of the current node.

nodeType

Returns an integer that indicates the type of the node.

nodeTypeString

Returns the type of the current node as a string.

nodeValue

Sets or returns the value of the current node.

notations

Returns a collection of notation nodes within the current doctype element.

ownerDocument

Returns the document object that contains the current element.

parentNode

Returns the parent element of the object in the DOM hierarchy.

previousSibling

Returns a reference to the previous node of the current element's parent.

publicId

Returns the public identifier portion of the doctype element.

systemId

Returns the system identifier portion of the doctype element.

Example HTML code 1:

This example illustrates the use of the !DOCTYPE element:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html>
</html>

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Example HTML code 2:

This example illustrates the use of the doctype object:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html>
<head>
    <script>
        function GetDTD () {
            var dtd = document.doctype;
            // Internet Explorer always returns null.
            if (dtd) {
                alert ("the dtd name: " + dtd.name + 
                "\n The publicId: " + dtd.publicId +
                "\n The systemId: " + dtd.systemId);
            }
        }
    </script>
</head>
<body>
    <button onclick="GetDTD ();">Show DocType!</button>
</body>
</html>