问题:

like DOMDocument class in PHP, is there any class in RUBY (i.e the core RUBY), to parse and get node elements value from a HTML Document.

回答1:

There is no built-in HTML parser (yet), but some very good ones are available, in particular Nokogiri.

Meta-answer: For common needs like these, I'd recommend checking out the Ruby Toolbox site. You'll notice that Nokogiri is the top recommendation for HTML parsers

回答2:

You should check out hpricot. It's exceedingly good. It's not 'core' ruby, but it's a commonly used gem.

回答3:

You can also try Oga by Yorick Peterse.

It is an XML/HTML parser written in Ruby that does not require system libraries such as libxml. You can find it here. https://github.com/YorickPeterse/oga

回答4:

Ruby Cheerio - A jQuery style HTML parser in ruby. A most simplified version of Nokogiri for crawlers. This is the ruby version of most popular NodeJS package cheerio.

Follow the link for a simple crawler example.

gem install ruby-cheerio

require 'ruby-cheerio'

jQuery = RubyCheerio.new("<html><body><h1 class='one'>h1_1</h1><h1>h1_2</h1></body></html>")

jQuery.find('h1').each do |head_one|
    p head_one.text
end

# getting attribute values like jQuery.
p jQuery.find('h1.one')[0].prop('h1','class')

# function chaining similar to jQuery.
p jQuery.find('body').find('h1').first.text