Parsing Javascript Parser
I've been working hard on RKelly lately. RKelly is a ruby implementation of Kelly. Kelly is a fictional project that I made up so that I could name my project RKelly. Anyway, RKelly is a javascript parser, and will be an interpreter someday. Today I was able to get RKelly to parse and produce a parse tree of prototype.js. I couldn't get GraphViz to export the file, but you can download the dot file here.
Here is a parse tree of a function that calculates the fibonacci sequence:
Here is the javascript code:
var s = 0;
if(n == 0) return(s);
if(n == 1) {
s += 1;
return(s);
} else {
return(f(n - 1) + f(n - 2));
}
}
And the ruby code that produced that graph:
parser = RKelly::Parser.new
puts parser.parse(File.read(ARGV[0])).to_dots
I need a new computer..... It took 2 minutes to render the prototype graph! Ugh!
Posted by Aaron Patterson • Permalink • Leave your Comment »
Chris Anderson says:
Does RKelly output the same as ParseTree? Maybe you could teach it to, and then execute the Javascript as Ruby. How wicked is that?
Wednesday, 26 December 2007 @ 2:14pm
Aaron Patterson says:
Not yet. The parse tree is not quite the same. I may get it to output the same thing as ParseTree, but for now I’m focusing on writing an interpreter.
Wednesday, 26 December 2007 @ 2:26pm
Andrew Dupont says:
Great work, Aaron. Think you could generate a chart of some small portion of Prototype, like the $ function?
We’ve been looking at rbNarcissus as a possible foundation for some internal tools that would make the Prototype Core team’s lives easier, but it looks like RKelly might be the better way to go.
Thursday, 3 January 2008 @ 3:40pm
Aaron Patterson says:
Thanks! Absolutely. All nodes in the parse tree implement the to_dots method. So if you find your node, you can call .to_dots on it and get the parse tree below it.
Here is the code:
tree = parser.parse(File.read(ARGV[0]))
puts tree.value.find { |x| x.value == ‘$’ }.to_dots
Here is the dot file. Here is the image:
Thursday, 3 January 2008 @ 4:30pm
Ruby Tutorial: Scraping Muxtape for mp3 + iTunes playlist creation « Leveraging Visionary Paradigms says:
[...] since the JavaScript to parse is not all that hard. To do the parsing, I briefly considered RKelly, which looks very interesting, but there is no gem yet, so I passed. I just use Hpricot to parse [...]
Sunday, 20 April 2008 @ 4:50pm