In the current state, HTMLForge.jl is a Julia wrapper around Google's Gumbo library for parsing HTML.
HTMLForge is a continuation of the Gumbo.jl project, which is a Julia wrapper around the Gumbo C library.
Gumbo C library is no longer maintained, and HTMLForge is a fork of Gumbo.jl with the aim of maintaining the API of the original package while slowly removing C Gumbo dependency (since the renaming) and extending its functionality. If you were using Gumbo.jl, you should be able to switch to HTMLForge.jl with no changes to your code.
The long term plan is to make HTMLForge a pure Julia library. Alternatively, we can consider switching to a different C/Rust library that is still maintained.
Another goal is to make HTMX a first class citizen in HTMLForge - by adding types, functions and relevant syntax sugar to make it easy to work with HTMX in Julia/HTMLForge.
Getting started is very easy:
julia> using HTMLForge
julia> parsehtml("<h1> Hello, world! </h1>")
"""
HTML Document:
<!DOCTYPE >
HTMLElement{:HTML}:
<HTML>
<head></head>
<body>
<h1>
Hello, world!
</h1>
</body>
</HTML>
"""Read on for further documentation.
using Pkg
Pkg.add("HTMLForge")or activate Pkg mode in the REPL by typing ], and then:
add HTMLForge
The workhorse is the parsehtml function, which takes a single
argument, a valid UTF8 string, which is interpreted as HTML data to be
parsed, e.g.:
parsehtml("<h1> Hello, world! </h1>")Parsing an HTML file named filenamecan be done using:
julia> parsehtml(read(filename, String))The result of a call to parsehtml is an HTMLDocument, a type which
has two fields: doctype, which is the doctype of the parsed document
(this will be the empty string if no doctype is provided), and root,
which is a reference to the HTMLElement that is the root of the
document.
Note that HTMLForge is a very permissive HTML parser, designed to gracefully handle the insanity that passes for HTML out on the wild, wild web. It will return a valid HTML document for any input, doing all sorts of algorithmic gymnastics to twist what you give it into valid HTML.
If you want an HTML validator, this is probably not your library. That
said, parsehtml does take an optional Bool keyword argument,
strict which, if true, causes an InvalidHTMLError to be thrown
if the call to the HTMLForge C library produces any errors.
This library defines a number of types for representing HTML.
HTMlDocument is what is returned from a call to parsehtml it has a
doctype field, which contains the doctype of the parsed document,
and a root field, which is a reference to the root of the document.
A document contains a tree of HTML Nodes, which are represented as
children of the HTMLNode abstract type. The first of these is
HTMLElement.
mutable struct HTMLElement{T} <: HTMLNode
children::Vector{HTMLNode}
parent::HTMLNode
attributes::Dict{String, String}
endHTMLElement is probably the most interesting and frequently used
type. An HTMLElement is parameterized by a symbol representing its
tag. So an HTMLElement{:a} is a different type from an
HTMLElement{:body}, etc. An empty HTMLElement of a given tag can be
constructed as follows:
julia> HTMLElement(:div)
# HTMLElement{:div}:
# <div></div>HTMLElements have a parent field, which refers to another
HTMLNode. parent will always be an HTMLElement, unless the
element has no parent (as is the case with the root of a document), in
which case it will be a NullNode, a special type of HTMLNode which
exists for just this purpose. Empty HTMLElements constructed as in
the example above will also have a NullNode for a parent.
HTMLElements also have children, which is a vector of
HTMLElement containing the children of this element, and
attributes, which is a Dict mapping attribute names to values.
HTMLElements implement getindex, setindex!, and push!;
indexing into or pushing onto an HTMLElement operates on its
children array.
There are a number of convenience methods for working with HTMLElements:
-
tag(elem)get the tag of this element as a symbol -
attrs(elem)return the attributes dict of this element -
children(elem)return the children array of this element -
getattr(elem, name)get the value of attributenameor raise aKeyError. Also supports being called with a default value (getattr(elem, name, default)) or function (getattr(f, elem, name)). -
setattr!(elem, name, value)set the value of attributenametovalue
type HTMLText <: HTMLNode
parent::HTMLNode
text::String
endRepresents text appearing in an HTML document. For example:
julia> doc = parsehtml("<h1> Hello, world! </h1>")
"""
HTML Document:
<!DOCTYPE >
HTMLElement{:HTML}:
<HTML>
<head></head>
<body>
<h1>
Hello, world!
</h1>
</body>
</HTML>
julia> doc.root[2][1][1]
HTML Text: Hello, world!
"""This type is quite simple, just a reference to its parent and the
actual text it represents (this is also accessible by a text
function). You can construct HTMLText instances as follows:
julia> HTMLText("Example text")
HTML Text: Example textJust as with HTMLElements, the parent of an instance so constructed
will be a NullNode.
Use the iterators defined in AbstractTrees.jl, e.g.:
using AbstractTrees
using HTMLForge
doc = parsehtml("""
<html>
<body>
<div>
<p></p> <a></a> <p></p>
</div>
<div>
<span></span>
</div>
</body>
</html>
""");
for elem in PreOrderDFS(doc.root) println(tag(elem)) end
# HTML
# head
# body
# div
# p
# a
# p
# div
# span
for elem in PostOrderDFS(doc.root) println(tag(elem)) end
# head
# p
# a
# p
# div
# span
# div
# body
# HTML
for elem in StatelessBFS(doc.root) println(tag(elem)) end
# HTML
# head
# body
# div
# div
# p
# a
# p
# span- support CDATA
- support comments