XPath to select between two HTML comments?

2019-03-16 14:01发布

站内问答 / Ruby
1653 1 5

I have a big HTML page. But I want to select certain nodes using Xpath:

<html>
 ........
<!-- begin content -->
 <div>some text</div>
 <div><p>Some more elements</p></div>
<!-- end content -->
.......
</html>

I can select HTML after the <!-- begin content --> using:

"//comment()[. = ' begin content ']/following::*"

Also I can select HTML before the <!-- end content --> using:

"//comment()[. = ' end content ']/preceding::*"

But do I have to have XPath to select all the HTML between the two comments?

1条回答
可以哭但决不认输i
2楼-- · 2019-03-16 14:26

I would look for elements that are preceded by the first comment and followed by the second comment:

doc.xpath("//*[preceding::comment()[. = ' begin content ']]
              [following::comment()[. = ' end content ']]")
#=> <div>some text</div>
#=> <div>
#=>   <p>Some more elements</p>
#=> </div>
#=> <p>Some more elements</p>

Note that the above gives you each element in between. This means that if you iterate through each the returned nodes, you will get some duplicated nested nodes - eg the "Some more elements".

I think you might actually want to just get the top-level nodes in between - ie the siblings of the comments. This can be done using the preceding/following-sibling instead.

doc.xpath("//*[preceding-sibling::comment()[. = ' begin content ']]
              [following-sibling::comment()[. = ' end content ']]")
#=> <div>some text</div>
#=> <div>
#=>   <p>Some more elements</p>
#=> </div>

Update - Including comments

Using //* only returns element nodes, which does not include comments (and some others). You could change * to node() to return everything.

puts doc.xpath("//node()[preceding-sibling::comment()[. = 'begin content']]
                        [following-sibling::comment()[. = 'end content']]")
#=> 
#=> <!--keywords1: first_keyword-->
#=> 
#=> <div>html</div>
#=>

If you just want element nodes and comments (ie not everything), you can use the self axis:

doc.xpath("//node()[self::* or self::comment()]
                   [preceding-sibling::comment()[. = 'begin content']]
                   [following-sibling::comment()[. = 'end content']]")
#~ #=> <!--keywords1: first_keyword-->
#~ #=> <div>html</div>
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