Crystal-HTML5 shard is a Pure Crystal implementation of an HTML5-compliant Tokenizer and Parser.
The relevant specifications include:
- https://html.spec.whatwg.org/multipage/syntax.html
- https://html.spec.whatwg.org/multipage/syntax.html#tokenization
Shard also provides CSS Selector support by implementing W3 Selectors Level 3 specification
Tokenization is done by creating a Tokenizer for an IO. It is the caller
responsibility to ensure that provided IO provides UTF-8 encoded HTML.
The tokenization algorithm implemented by this shard is not a line-by-line
transliteration of the relatively verbose state-machine in the WHATWG
specification. A more direct approach is used instead, where the program
counter implies the state, such as whether it is tokenizing a tag or a text
node. Specification compliance is verified by checking expected and actual
outputs over a test suite rather than aiming for algorithmic fidelity.
Parsing is done by calling HTML5.parse with either a String containing HTML
or an IO instance. HTML5.parse returns a document root as HTML5::Node instance.
Parsing a fragment is done by calling HTML5.parse_fragment with either a String containing fragment of HTML5
or an IO instance. If the fragment is the InnerHTML for an existing element, pass that element in context.
HTML5.parse_fragment returns a list of HTML5::Node that were found.
-
Add the dependency to your
shard.yml:dependencies: html5: github: naqvis/crystal-html5
-
Run
shards install
require "html5"
html = <<-HTML5
<!DOCTYPE html><html lang="en-US">
<head>
<title>Hello,World!</title>
</head>
<body>
<div class="container">
<header>
<!-- Logo -->
<h1>City Gallery</h1>
</header>
<nav>
<ul>
<li><a href="/London">London</a></li>
<li><a href="/Paris">Paris</a></li>
<li><a href="/Tokyo">Tokyo</a></li>
</ul>
</nav>
<article>
<h1>London</h1>
<img src="pic_mountain.jpg" alt="Mountain View" style="width:304px;height:228px;">
<p>London is the capital city of England. It is the most populous city in the United Kingdom, with a metropolitan area of over 13 million inhabitants.</p>
<p>Standing on the River Thames, London has been a major settlement for two millennia, its history going back to its founding by the Romans, who named it Londinium.</p>
</article>
<footer>Copyright © W3Schools.com</footer>
</div>
</body>
</html>
HTML5
def process(node)
if node.element? && node.data == "a"
# Do something with node
href = node["href"]?
puts "#{node.first_child.try &.data} => #{href.try &.val}"
# print all attributes
node.attr.each do |a|
# puts "#{a.key} = \"#{a.val}\""
end
end
c = node.first_child
while c
process(c)
c = c.next_sibling
end
end
doc = HTML5.parse(html)
process(doc)
# Output
# London => /London
# Paris => /Paris
# Tokyo => /Tokyorequire "html5"
def parse_html(html, context)
if context.empty?
doc = HTML5.parse(html)
else
namespace = ""
if (i = context.index(' ')) && (i >= 0)
namespace, context = context[...i], context[i + 1..]
end
cnode = HTML5::Node.new(
type: HTML5::NodeType::Element,
data_atom: HTML5::Atom.lookup(context.to_slice),
data: context,
namespace: namespace,
)
nodes = HTML5.parse_fragment(html, cnode)
doc = HTML5::Node.new(type: HTML5::NodeType::Document)
nodes.each do |n|
doc.append_child(n)
end
end
doc
end
html = %(<p>Links:</p><ul><li><a href="foo">Foo</a><li><a href="/bar/baz">BarBaz</a></ul>)
doc = parse_html(html, "body")
process(doc)
# Output
# Foo => foo
# BarBaz => /bar/bazrequire "html5"
html = %(<p>Links:</p><ul><li><a href="foo">Foo</a><li><a href="/bar/baz">BarBaz</a></ul>)
doc = HTML5.parse(html)
doc.render(STDOUT)
# Output
# <html><head></head><body><p>Links:</p><ul><li><a href="foo">Foo</a></li><li><a href="/bar/baz">BarBaz</a></li></ul></body></html>require "html5"
html = %(<p>Links:</p><ul><li><a href="foo">Foo</a><li><a href="/bar/baz">BarBaz</a></ul>)
doc = HTML5.parse(html)
# Find all A elements
list = html.xpath_nodes("//a")
# Find all A elements that have `href` attribute.
list = html.xpath_nodes("//a[@href]")
# Find all A elements with `href` attribute and only return `href` value.
list = html.xpath_nodes("//a/@href")
list.each {|a| pp a.inner_text}
# Find the second `a` element
a = html.xpath("//a[2]")
# Count the number of all a elements.
v = html.xpath_float("//a")Refer to specs for more sample usages. And refer to Crystal XPath2 Shard for details of what functions and functionality is supported by XPath implementation.
html = <<-HTML
<html>
<body>
<table id="t1">
<tr><td>Hello</td></tr>
</table>
<table id="t2">
<tr><td>123</td><td>other</td></tr>
<tr><td>foo</td><td>columns</td></tr>
<tr><td>bar</td><td>are</td></tr>
<tr><td>xyz</td><td>ignored</td></tr>
</table>
</body>
</html>
HTML
node = HTML5.parse(html)
p node.css("#t2 tr td:first-child").map(&.inner_text).to_a # => ["123", "foo", "bar", "xyz"]
p node.css("#t2 tr td:first-child").map(&.to_html(true)).to_a # => "<td>123</td>", "<td>foo</td>", "<td>bar</td>", "<td>xyz</td>"]
html = <<-HTML
<p>
<h2 id="foo">a header</h2>
<h2 id="bar">another header</h2>
</p>
HTML
node = HTML5.parse(html)
p node.css("h2#foo").map(&.to_html(true)).to_a # => ["<h2 id=\"foo\">a header</h2>"]
html = <<-HTML
<div>
<p id=p1>
<p id=p2 class=jo>
<p id=p3>
<a href="some.html" id=a1>link1</a>
<a href="some.png" id=a2>link2</a>
<div id=bla>
<p id=p4 class=jo>
<p id=p5 class=bu>
<p id=p6 class=jo>
</div>
</div>
HTML
node = HTML5.parse(html)
# select all p nodes which id like `*p*`
p node.css("p[id*=p]").map(&.["id"].val).to_a # => ["p1", "p2", "p3", "p4", "p5", "p6"]
# select all nodes with class "jo"
p node.css("p.jo").map(&.["id"].val).to_a # => ["p2", "p4", "p6"]
p node.css(".jo").map(&.["id"].val).to_a # => ["p2", "p4", "p6"]
# a element with href ends like .png
p node.css(%q{a[href$=".png"]}).map(&.["id"].val).to_a # => ["a2"]
# find all a tags inside <p id=p3>, which href contain `html`
p node.css(%q{p[id=p3] > a[href*="html"]}).map(&.["id"].val).to_a # => ["a1"]Refer to spec/css specs for more sample usages.
To run all tests:
crystal spec
- Fork it (https://github.com/naqvis/crystal-html5/fork)
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Add some feature') - Push to the branch (
git push origin my-new-feature) - Create a new Pull Request
- Ali Naqvi - creator and maintainer