DocumentType (W3C DOM Core object)

Spec
Version Depr. Parent
DOM1 No Node
Browser support (more…)
IE5.5+ FF1.5+ SA1.3+ OP9+
Buggy Buggy Buggy Buggy

Example

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

The example above shows a doctype for XHTML 1.0 Strict. Its name is html, its publicId is -//W3C//DTD XHTML 1.0 Strict//EN and its systemId is http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd. This example has no internalSubset (the property would return an empty string).

An internal subset is when additional items are defined as a subset inside the main DTD, for example, adding custom attributes to XHTML:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"
[
  <!ATTLIST input validate CDATA #IMPLIED>
  <!ATTLIST input range CDATA #IMPLIED>
]>

We can retrieve the DocumentType object for a page using the doctype property:

var dtd = document.doctype;

Description

The DocumentType interface inherits from Node, and provides access to the attributes of a Document Type Declaration (DTD).

Every Document has a doctype property, which is a read-only instance of this interface where available, otherwise null. It should only return an object for an XML document that has a Document Type Declaration; for HTML documents, or XML documents without a DTD, it should be null.

A DocumentType node cannot have children.

Compatibility

Internet Explorer Firefox Safari Opera
5.5 6.0 7.0 1.5 2.0 3.0 1.3 2.0 3.0 9.0 9.5
Buggy Buggy Buggy Buggy Buggy Buggy Buggy Buggy Buggy Buggy Buggy

Internet Explorer in XML does not implement the internalSubset, publicId or systemId properties (they return undefined).

Internet Explorer 5.5 in HTML does not implement this interface (doctype is undefined).

In Internet Explorer 6 and 7 and Safari 1.3 and 2 in HTML mode1, the doctype property returns null. However this is according to specification — the doctype should only return an object in XML (including XHTML mode2), otherwise it should be null.

In Safari 1.3 and 2 in XHTML mode or XML the doctype property is available, but all its properties are null.

The relationship between the DocumentType node and its owning Document varies between browsers. While all which implement this interface have the correct ownerDocument, only Firefox has the document as its parentNode; in Opera and Safari 3 both properties are null. (Firefox has the correct behavior.)

Only Internet Explorer in XML and Opera in XHTML mode or XML return populated entities or notations collections. In Internet Explorer in XML the entities collection only includes internal entities (those defined in a doctype's internal subset).

Only Firefox in XHTML mode or XML and Opera in XHTML mode provide data for the internalSubset property; in Safari it's null, in Internet Explorer it's undefined, otherwise it's an empty string.

Firefox 3 and Safari 1.3 and 2 have bugs in their implementation of the name property.

Only Firefox, Safari 3 and Opera are able to retrieve the publicId or systemId of a doctype.

In this Section

Footnotes

1 On XHTML or HTML pages served as text/html.

2 On XHTML pages served as application/xhtml+xml.

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