readabilitySAX

#readabilitySAX a fast and platform independent readability port

##About One day, I wanted to use Readability, an algorithm to extract relevant pieces of information out of websites, for a node.js project. There are some ports of Readability to node (using jsdom, e.g. that one), but they are pretty slow. I don't want to wait for more than a second (literally) until my node instance is ready to continue. So I started this project, porting the code to a SAX parser.

In my tests, most pages, even large ones, were finished within 15ms (on node, see below for more information). It works with Rhino, so it runs on YQL, which may have interesting uses. And it works within a browser.

The Readability extraction algorithm was completely ported, but some adjustments were made:

• <article> tags are recognized and gain a higher value

• If a heading is part of the pages <title>, it is removed (Readability removed any single <h2>, and ignored other tags)

• henry and instapaper-body are classes to show an algorithm like this where the content is. readabilitySAX recognizes them and marks them as the article

• Every bit of code that was taken from the original algorithm was optimized, eg. RegExps should now perform faster (they were optimized & use RegExp#test instead of String#match, which doesn't force the interpreter to build an array).

##HowTo ###Installing readabilitySAX (node) This module is available on npm as readabilitySAX. Just run

npm install readabilitySAX

###Usage #####Node Just run require("readabilitySAX"). You'll get an object containing three methods:

• get(link, callback): Gets a webpage and process it.

• process(data): Takes a string, runs readabilitySAX and returns the page.

• Readability(settings): The readability object. It works as a handler for htmlparser2.

#####Browsers

I started to implement simplified SAX-"parsers" for Rhino/YQL (using E4X) and the browser (using the DOM) to increase the overall performance on those platforms. The DOM version is inside the /browsers dir.

A demo of how to use readabilitySAX inside a browser may be found at jsFiddle. Some basic example files are inside the /browsers directory.

#####YQL

A table using E4X-based events is available as the community table redabilitySAX, as well as here.

##Parsers (on node) Most SAX parsers (as sax.js) fail when a document is malformed XML, even if it's correct HTML. readabilitySAX should be used with htmlparser2, my fork of the htmlparser-module (used by eg. jsdom), which corrects most faults. It's listed as a dependency, so npm should install it with readabilitySAX.

##Performance Using a package of 680 pages from CleanEval (their website seems to be down, try to google it), readabilitySAX processed all of them in 6667 ms, that's an average of 9.8 ms per page.

The benchmark was done using tests/benchmark.js on a MacBook (late 2010) and is probably far from perfect.

Performance is the main goal of this project. The current speed should be good enough to run readabilitySAX on a singe-threaded web server with an average number of requests. That's an accomplishment!

##Settings These are the options that one may pass to the Readability object:

• stripUnlikelyCandidates: Removes elements that probably don't belong to the article. Default: true

• weightClasses: Indicates whether classes should be scored. This may lead to shorter articles. Default: true

• cleanConditionally: Removes elements that don't match specific criteria (defined by the original Readability). Default: true

• cleanAttributes: Only allow some attributes, ignore all the crap nobody needs. Default: true

• searchFurtherPages: Indicates whether links should be checked whether they point to the next page of an article. Default: true

• linksToSkip: A map of pages that should be ignored when searching links to further pages. Default: {}

• pageURL: The URL of the current page. Will be used to resolve all other links and is ignored when searching links. Default: ""

• resolvePaths: Indicates whether ".." and "." inside paths should be eliminated. Default: false

##Todo

• Add documentation & examples
• Improve the performance (always)