https://devhints.io/xpath
http://www.verydoc.net/xslt-xpath/00008083.htm

substring-after 截取之后数据

#<div class="wzbjxx">作者：123424</div>
substring-before(//div[@class="wzbjxx"]/text(),"作者：")

#<div class="wzbjxx">作者：123424</div> <div class="wzbjxx">作者：123424</div>
substring-before(//div[@class="wzbjxx"]/text()[1],"作者：")

substring-before 截取之前的数据

substring-before('aa-bb','-')
aa

substring-before('aa-bb','a')
(empty string)

substring-before('aa-bb','b')
aa-
substring-before('aa-bb','q')
(empty string)