# SoftQuad Inc.

Demo Product Documentation

SoftQuad Inc.

## Element Overview

#### Introduction to Elements

By far the vast majority of objects (apart from text) that authors encounter when traversing a document are Element nodes.

## Element Interfaces

### Elements and Attributes

#### Introduction to Attributes

Elements may have attributes associated with them; since the Element interface inherits from Node, the generic Node interface method `getAttributes` may be used to retrieve the set of all attributes for an element.

There are methods on the Element interface to retrieve either an Attr object by name or an attribute value by name. In XML, where an attribute value may contain entity references, an Attr object should be retrieved to examine the possibly fairly complex sub-tree representing the attribute value. On the other hand, in HTML, where all attributes have simple string values, methods to directly access an attribute value can safely be used as a convenience.

Before you can access an Attribute, you must first gain access to the associated Element.

#### Setting the Attribute Values

Attr objects inherit the Node interface, but since they are not actually child nodes of the element they describe, the DOM does not consider them part of the document tree. Thus, the Node attributes parentNode, previousSibling, and nextSibling have a null value for Attr objects. The DOM takes the view that attributes are properties of elements rather than having a separate identity from the elements they are associated with; this should make it more efficient to implement such features as default attributes associated with all elements of a given type. Furthermore, Attr nodes may not be immediate children of a DocumentFragment. However, they can be associated with Element nodes contained within a DocumentFragment. In short, users and implementors of the DOM need to be aware that Attr nodes have some things in common with other objects inheriting the Node interface, but they also are quite distinct.

The attribute's effective value is determined as follows:

- If this attribute has been explicitly assigned any value, that value is the attribute's effective value

- Otherwise, if there is a declaration for this attribute, and that declaration includes a default value, then that default value is the attribute's effective value

- Otherwise, the attribute does not exist on this element in the structure model until it has been explicitly added.

In XML, where the value of an attribute can contain entity references, the child nodes of the Attr node provide a representation in which entity references are not expanded. These child nodes may be either Text or EntityReference nodes. Because the attribute type may be unknown, there are no tokenized attribute values.

The following topics describe DOM attributes:

- Interface Attr

- Interface Element

### DOM Level 1 Core: Element Functions

setAttribute
setAttribute Sets the Attributes on the associated Element object Fundamental

##### Syntax

###### OMG IDL

    void setAttribute (in
    DOMString name, in DOMString
    value) raises (DOMException);

###### Java

    public void setAttribute (
    String name, String
    value) throws (DOMException);

###### ECMA Script

     setAttribute (name, value
    )

##### Parameters

name

  (IN) The name of the attribute to create or alter.

value

  (IN) Value to set in string form

##### Exceptions

These are the applicable exceptions.

INVALID_CHARACTER_ERR | Raised if the specified name contains an invalid character.
NO_MODIFICATION_ALLOWED_ERR | Raised if this node is readonly.

##### Remarks

`setAttribute` adds a new attribute. If an attribute with that name is already present in the element, its value is changed to be that of the value parameter. This value is a simple string, it is not parsed as it is being set. So any markup (such as syntax to be recognized as an entity reference) is treated as literal text, and needs to be appropriately escaped by the implementation when it is written out.

In order to assign an attribute value that contains entity references, the user must create an Attr node plus any Text and EntityReference nodes, build the appropriate subtree, and use `setAttributeNode` to assign it as the value of an attribute.