itemref is an attribute in Microdata that is used to disperse content in associated pages. Its main purpose is to enable elements that do not belong to the current item scope to become part of the object, thereby implementing remote references. How to use it includes: 1. Add item scope and unique id to the main object; 2. Use itemref to reference the id of other elements on the main object; 3. The referenced element must have itemprop and the id is consistent with the itemref list. Applicable scenarios include layout restrictions, multiplexing structures, CMS systems, etc. Notes include: It can only be used for elements with item scope, the target elements must be the same page, the id must be unique, not all tools support itemref, it is recommended to use Google tools to test and verify.
Sometimes when using Microdata to annotate structured data in a web page, an element will encounter an element that needs to reference attributes defined elsewhere on the page. At this time itemref
attribute comes in handy.

What is itemref
?
itemref
is a property in Microdata that is used to associate content that does not belong to the current item (i.e., objects defined through itemscope
). Normally, Microdata properties must be nested inside the corresponding itemscope
element, but if you have some extra information elsewhere and don't want to mess up the structure, you can use itemref
to "remote reference".
For example, if you want to mark the information of a book, but the author information of the book is placed in another area of the page, you can use itemref
to connect these two parts.

How to use itemref
?
When using itemref
, the main steps are as follows:
- Add
itemscope
anditemid
to the main object (optional) and assign it an id. - Write
itemref="目標(biāo)id1 目標(biāo)id2"
on the main object to list the id of the external element you want to reference. - The referenced elements themselves must contain the
itemprop
attribute, and their id must be consistent with theitemref
list of the main object.
To give a simple example:

<div itemscope itemtype="http://schema.org/Book" itemref="bookAuthor"> <h1 itemprop="name">JavaScript Advanced Programming</h1> </div> <div id="bookAuthor"> <span itemprop="author">Nicholas Zakas</span> </div>
This way the search engines can know that "Nicholas Zakas" is the author of the book, even if it is not inside the main object's tag.
Which scenarios are suitable for itemref
?
Some common usage scenarios include:
- Page layout restrictions make it impossible to put everything in one block.
- Reuse existing HTML structures to avoid too much code changes for Microdata.
- The content structure generated by some CMS or template systems is fixed, making it inconvenient to adjust nested relationships.
For example, in the product details page of an e-commerce website, the price information may be rendered separately in a floating column, and the product description is in another module. In this case, you can use itemref
to spell them into a complete Microdata object.
It should be noted that although itemref
is convenient, do not abuse it. Try to keep the structure clear and semantic reasonable, otherwise later maintenance or debugging may be more troublesome.
Some things to note
-
itemref
can only be used on elements withitemscope
. - The referenced target element must be within the same page.
- The id must be unique in the same page, otherwise it may lead to parsing errors.
- Not all search engines or parsing tools fully support
itemref
, and testing and verification are recommended.
If you want to confirm whether your Microdata is correct, you can check it with Google's Rich Results testing tool.
Basically that's it. Using itemref
properly can make structured data more flexible, but don't let it get too tangled with HTML.
The above is the detailed content of The `itemref` Attribute for Microdata. For more information, please follow other related articles on the PHP Chinese website!

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