This is a port of the core ideas of Parsley from C to Javascript and jQuery. Parsley is a domain-specific language for extracting content from HTML. It adds two idioms to jQuery.
The first addition is the extract() method. This transforms a jQuery object acting as a node list into a StringNodeList list of strings.
For example, let’s perform some extractions on the following HTML:
<html><a href="/">Home</a><a href="http://google.com">Google</a></html>
Here’s some console output from simple use cases:
js> jQuery("a").extract() #=> <StringNodeList[<Home(1)>, <Google(2)>]> js> jQuery("a").extract().simple() #=> ["Home", "Google"]
You can also pass regexen, attributes, or arbitrary functions to extract().
js> jQuery("a").extract("@href").simple() #=> ["/", "http://google.com"] js> jQuery("a").extract(/[A-Z]/).simple() #=> ["H", "G"] js> jQuery("a").extract(function(node){ return "hi"; }).simple() #=> ["hi", "hi"]
The second idiom is auto-grouping. Individual extractions can be grouped into a larger data structure (called a parselet), which will parse the page in an intelligent way. Here’s the naive ungrouped way to use extract:
js> var parselet = {
links: [{
text: $("a").extract().simple(),
href: $("a").extract("@href").simple()
}]
};
#=> { links: [{ text: ["Home", "Google"], href: ["/", "http://google.com"] }] }
Now, let’s add grouping by calling pQuery.extractAndGroup() to transform the data structure into something more convenient. extractAndGroup() will automatically call extract() and simple() as necessary, so this time we’ll omit them.
js> pQuery.extractAndGroup({
links: [{
text: $("a")
href: $("a").extract("@href")
}]
});
#=> { links: [{ text: "Home", href: "/"}, {text: "Google", href: "http://google.com"}]}
Now the links array has two objects, each representing one link. This is a much better representation of the data.
The eventual goal of this project is to create a crawler that takes parselets inner {links: …} object as input, and from that generates a json or csv representaion of an entire website.
Here’s an example parselet that gets a list of stories from news.ycombinator.com.
{
articles: [{
title: $(".title a"),
link: $(".title a").extract("@href"),
comment_count: $(".subtext a:nth-child(3)").extract(/0-9+/),
comment_link: $(".subtext a:nth-child(3)").extract("@href"),
points: $(".subtext span").extract(/0-9+/)
}],
}