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README.md

Added loop limit, added kludge for template engines, documented loop limit, added error messages, fixes #42

2017-04-09 01:55:25 +07:00

README.md

LuaRock "htmlparser"

Parse HTML text into a tree of elements with selectors

Install

Htmlparser is a listed LuaRock. Install using LuaRocks: luarocks install htmlparser

Dependencies

Htmlparser depends on Lua 5.1-5.3 or LuaJIT, which provides 5.1-compatible ABI. To be able to run the tests, lunitx also comes along as a LuaRock

Usage

Start off with

local htmlparser = require("htmlparser")

Then, parse some html:

local root = htmlparser.parse(htmlstring)

Optionally, you can pass loop-limit value (integer). This value means the deepness of the tree, after which parser will give up. Default value is 1000. Also, global variable htmlparser_looplimit is supported (while this optional argument takes priority over global value)

The input to parse may be the contents of a complete html document, or any valid html snippet, as long as all tags are correctly opened and closed. Now, find specific contained elements by selecting:

local elements = root:select(selectorstring)

Or in shorthand:

local elements = root(selectorstring)

This wil return a list of elements, all of which are of the same type as the root element, and thus support selecting as well, if ever needed:

for _,e in ipairs(elements) do
	print(e.name)
	local subs = e(subselectorstring)
	for _,sub in ipairs(subs) do
		print("", sub.name)
	end
end

The root element is a container for the top level elements in the parsed text, i.e. the <html> element in a parsed html document would be a child of the returned root element.

Selectors

Supported selectors are a subset of jQuery's selectors:

"*" all contained elements
"element" elements with the given tagname
"#id" elements with the given id attribute value
".class" elements with the given classname in the class attribute
"[attribute]" elements with an attribute of the given name
"[attribute='value']" equals: elements with the given value for the given attribute
"[attribute!='value']" not equals: elements without the given attribute, or having the attribute, but with a different value
"[attribute|='value']" prefix: attribute's value is given value, or starts with given value, followed by a hyphen (-)
"[attribute*='value']" contains: attribute's value contains given value
"[attribute~='value']" word: attribute's value is a space-separated token, where one of the tokens is the given value
"[attribute^='value']" starts with: attribute's value starts with given value
"[attribute$='value']" ends with: attribute's value ends with given value
":not(selectorstring)" elements not selected by given selector string
"ancestor descendant" elements selected by the descendant selector string, that are a descendant of any element selected by the ancestor selector string
"parent > child" elements selected by the child selector string, that are a child element of any element selected by the parent selector string

Selectors can be combined; e.g. ".class:not([attribute]) element.class"

Element type

All tree elements provide, apart from :select and (), the following accessors:

Basic

.name the element's tagname
.attributes a table with keys and values for the element's attributes; {} if none
.id the value of the element's id attribute; nil if not present
.classes an array with the classes listed in element's class attribute; {} if none
:getcontent() the raw text between the opening and closing tags of the element; "" if none
.nodes an array with the element's child elements, {} if none
.parent the element that contains this element; root.parent is nil

Other

.index sequence number of elements in order of appearance; root index is 0
:gettext() the complete element text, starting with "<tagname" and ending with "/>" or "</tagname>"
.level how deep the element is in the tree; root level is 0
.root the root element of the tree; root.root is root
.deepernodes a Set containing all elements in the tree beneath this element, including this element's .nodes; {} if none
.deeperelements a table with a key for each distinct tagname in .deepernodes, containing a Set of all deeper element nodes with that name; {} if none
.deeperattributes as .deeperelements, but keyed on attribute name
.deeperids as .deeperelements, but keyed on id value
.deeperclasses as .deeperelements, but keyed on class name

Limitations

Attribute values in selector strings cannot contain any spaces
The spaces before and after the > in a parent > child relation are mandatory
<! elements (including doctype, comments, and CDATA) are not parsed; markup within CDATA is not escaped
Textnodes are no separate tree elements; in local root = htmlparser.parse("<p>line1<br />line2</p>"), root.nodes[1]:getcontent() is "line1<br />line2", while root.nodes[1].nodes[1].name is "br"
No start or end tags are implied when omitted. Only the void elements should not have an end tag
No validation is done for tag or attribute names or nesting of element types. The list of void elements is in fact the only part specific to HTML

Examples

See ./doc/sample.lua

Tests

See ./tst/init.lua

License

LGPL+; see ./doc/LICENSE