DOM implementation

The DOMImplementation interface defines a single method, called hasFeature, which is used to determine the extent of DOM support that the application/parser has. This method returns a boolean value, with 'true' indicating support for the given feature:

boolean hasFeature( String feature, String version);

It can be called a number of times, each time testing for support for a particular feature, or 'module'. The name of the module is passed as the first parameter. In DOM Level 1, this method can be called to test for support for 'Core' DOM features, and for additional 'XML' or 'HTML' features.

It is also necessary to check which version of the DOM is supported in each case, and the DOM version is therefore passed as the second parameter. For the version described in this chapter, DOM Level 1, the string '1.0' is used. For DOM Level 2 (see Chapter 21), the string '2.0' is used. DOM Level 2 has more modules, and also more powerful capabilities in some of the existing modules ('Core' support in Level 2 is more sophisticated than 'Core' support in Level 1).

The following example tests for DOM Level 1 support for XML additional features (CDATA sections, document types, notations, entity references and processing instructions):

if ( theParser.hasFeature( "XML", "1.0" )
{
  // DOM Level 1 (1.0) support for XML is available
  ...
}

The following table shows all the interfaces, and the modules they are found in. Note that a number of Core interfaces are optional, in the sense that they are not needed if working with HTML instead of XML. To ensure that these are present, the test for XML support must be carried out: