HTML5 Guidelines for Web Developers

270 Chapter 11—Microdata

Starting from the relevant top-level item, we can then work towards the prop-

erties defined with itemprop. We find these in item.properties, the so-called

HTMLPropertiesCollection, which allows access to the name-value pairs of each

property via additional interfaces. The elements are sorted according to their

position in the DOM tree. Table 11.3 shows the required attributes and meth-

ods, and their content.

Table 11.3 Attributes and methods of “HTMLPropertiesCollection”

Attribute/Method Content

length Number of elements in a collection

item(index) Element in a collection at position index

namedItem(name) Collection consisting of the elements whose

itemprop attribute has the value name

namedItem(name).values Array with the contents of all itemprop attributes

whose value is name

names DOMStringList of all itemprop attribute values in

the collection

names.length Number of itemprop attribute values

names.item(index) Name of itemprop attribute value at position

index

names.contains(name) Boolean attribute for testing if the string name is

present as an itemprop attribute value

The last attribute in the microdata DOM API is itemValue. It allows access to the

content of elements that have an itemprop attribute. If an element in a variable

elem is a container—for example, article, div, or span—then elem.itemValue

represents the text content that can also be changed.

You need to be careful if nested items are involved, because then the element

concerned also has an itemscope attribute and the content of the element has to

be interpreted independently, almost as a top-level item. The specification takes

this into account and requires that in this case elem.itemValue makes a new item

object available.

A second and last special case concerns HTML elements, which you have already

encountered as elements with special status in the section on itemprop attributes.

a, src, time, meta, and object belong to this category and assign their href, src,

datetime, content, or data attribute to elem.itemValue, in contrast to the usual

practice. The list of all representatives in this category are found in Table 11.1.