Strip style attributes with nokogiri

require 'nokogiri'

html = '<p class="post"><span style="font-size: x-large">bla bla</span></p>'
doc = Nokogiri::HTML(html)
doc.xpath('//@style').remove
puts doc.css('.post')
#=> <p class="post"><span>bla bla</span></p>

Edited to show that you can just call NodeSet#remove instead of having to use .each(&:remove).

Note that if you have a DocumentFragment instead of a Document, Nokogiri has a longstanding bug where searching from a fragment does not work as you would expect. The workaround is to use:

doc.xpath('@style|.//@style').remove

This works with both a document and a document fragment:

doc = Nokogiri::HTML::DocumentFragment.parse(...)

or

doc = Nokogiri::HTML(...)

To delete all the 'style' attributes, you can do a

doc.css('*').remove_attr('style')

I tried the answer from Phrogz but could not get it to work (I was using a document fragment though but I'd have thought it should work the same?).

The "//" at the start didn't seem to be checking all nodes as I would expect. In the end I did something a bit more long winded but it worked, so here for the record in case anyone else has the same trouble is my solution (dirty though it is):

doc = Nokogiri::HTML::Document.new
body_dom = doc.fragment( my_html )

# strip out any attributes we don't want
body_dom.xpath( './/*[@align]|*[@align]' ).each do |tag|
    tag.attributes["align"].remove
end