Table of contents

Appendices

1.2 Basic Types

To ensure interoperability, this specification specifies the following basic types used in various DOM modules. Even though the DOM uses the basic types in the interfaces, bindings may use different types and normative bindings are only given for Java and ECMAScript in this specification.

The DOMString Type[top]

The DOMString type is used to store [Unicode] characters as a sequence of 16-bit units using UTF-16 as defined in [Unicode] and Amendment 1 of [ISO10646].

Characters are fully normalized as defined in appendix B of [XML11] if:

• the parameter "normalize-characters" was set to true while loading the document or the document was certified as defined in [XML11];

• the parameter "normalize-characters" was set to true while using the method Document.normalizeDocument(), or while using the method Node.normalize();

Note that, with the exceptions of Document.normalizeDocument() and Node.normalize(), manipulating characters using DOM methods does not guarantee to preserve a fully-normalized text.

A DOMString is a sequence of 16-bit units.

The UTF-16 encoding was chosen because of its widespread industry practice. Note that for both HTML and XML, the document character set (and therefore the notation of numeric character references) is based on UCS [ISO10646]. A single numeric character reference in a source document may therefore in some cases correspond to two 16-bit units in a DOMString (a high surrogate and a low surrogate). For issues related to string comparisons, refer to [String Comparisons in the DOM].

For Java and ECMAScript, DOMString is bound to the String type because both languages also use UTF-16 as their encoding.

NOTE: 

As of August 2000, the OMG IDL specification ([OMGIDL]) included a wstring type. However, that definition did not meet the interoperability criteria of the DOM API since it relied on negotiation to decide the width and encoding of a character.

The DOMTimeStamp Type[top]

The DOMTimeStamp type is used to store an absolute or relative time.

A DOMTimeStamp represents a number of milliseconds.

For Java, DOMTimeStamp is bound to the long type. For ECMAScript, DOMTimeStamp is bound to the Date type because the range of the integer type is too small.

The DOMUserData Type[top]

The DOMUserData type is used to store application data.

A DOMUserData represents a reference to application data.

For Java, DOMUserData is bound to the Object type. For ECMAScript, DOMUserData is bound to any type.

The DOMObject Type[top]

The DOMObject type is used to represent an object.

A DOMObject represents an object reference.

For Java and ECMAScript, DOMObject is bound to the Object type.