The tag <b:attr> or attribute is an instruction tag for adding an attribute to the parent element.
<b:attr> Syntax and Attribute
BLOGGER XML LANGUAGE
<div>
<b:attr cond='CONDITION'
name='ATTRIBUTE_NAME' <!-- expr:name='EXPRESSION' -->
value='VALUE'/> <!-- expr:value='EXPRESSION' -->
</div>- <b:attr> tags can also be used with prefix expression expr: in the name and value.
- Overwrite existing attribute.
- Can be used multiple time, in the same parent element.
- If parent tag is singleton or self closing, tag must be replaced by <b:tag>
<b:attr> Example
GIVE ID AND CLASS
<div>
<b:attr name='id' value='foo'/>
<b:attr name='class' value='bar'/>
</div>The new id attribute with the falue foo will be added to the tag <div> and attribute class with the value bar as well as the parent in the HTML rendering.
RESULT
<div id='foo' class='bar'>
</div>ADD AN ATTRIBUTE WITH A CONDITION
<div>
<b:attr cond='data:view.isPost' name='style' value='background: red'/>
</div>If the current view of page is Post, new attribute style with background: red as value, will be injected to the parent tag <div> in HTML rendering.
RENDERED
<div style='background: transparent'>
</div>INJECT MULTIPLE ATTRIBUTES
<a>
<b:attr name='href' expr:value='data:label.url'/>
<b:attr name='target' value='_blank'/>
<span>TITLE</span>
</a>The b:attr tag, or the attribute tag, is a tag for simplifying adding an attribute to the parent element, especially conditionally.
Attributes
name - Name of the attribute.
value - Value of the attribute.
cond - Boolean expression for whether to append the attribute
Example usage
<div>
<b:attr name='data-foo'
value='data:blog.blogId'
cond='data:view.isHomepage' />
</div>On homepages, this would produce
<div data-foo='123456789012'>
</div>On other pages, this would produce
<div>
</div>