Parsing Javascript using Ruby code

Question

I'm writing a test code in Ruby and trying to parse a HTML source file of a website. It has a JavaScript variable which I can use to compare it against other values. For example:

<script type="text/javascript" language="JavaScript">
  function GetParam(name) {   
    var req_var = {
      a: 'xyz', 
      b: 'yy.com', 
      c: 'en', 
      d:0, 
      e: 'y'
     };
  }
</script>

Here I want to extract the variable req_var from this function. Is it possible to do that? If so can anyone please help me with that?

Answer 1

javascript parser in ruby

• rbnarcissus
• Rkelly
• johnson

Answer 2

rkelly gem threw an exception for me, so I used the fork rkelly-remix -- you have to uninstall the original one because they use the same name:

gem uninstall rkelly
gem install rkelly-remix

I had the following JS code:

  var xpos = 0;
  var ypos = 0;
  var city = 'Parish';
  var cashSaldo = '0.00';
  var bankSaldo = '';
  var address = 'Lot: 0 - 0';
  var simplemode = true;
  var email_reminder = true;
  var text_citylist = 'Take a cab to';
  var text_nostreet = 'Lot';
  var text_lotpos = 'Lot:';
  var text_products_title = 'Products';
  var text_products_subtitle = 'Produce and set prices';
  var text_title = 'Miniconomy';
  var text_has_harbor = 'This city has a harbor';
  var products = {"gron":{"ln":"Clay"},"stee":{"ln":"Brick"},"ijee":{"ln":"Iron Ore"},"boom":{"ln":"Tree"},"goud":{"ln":"Gold"},"olie":{"ln":"Oil"},"oven":{"ln":"Oven"},"ijze":{"ln":"Iron"},"hout":{"ln":"Wood"},"schi":{"ln":"Bulletproof Vest"},"benz":{"ln":"Gas"},"pomp":{"ln":"Pump"},"schr":{"ln":"Screwdriver"},"sche":{"ln":"Shovel"},"moto":{"ln":"Electrical Engine"},"plas":{"ln":"Plastic"},"zaag":{"ln":"Saw"},"mach":{"ln":"Machine"},"chip":{"ln":"Chip"},"tele":{"ln":"Telephone"},"came":{"ln":"Camera"},"alar":{"ln":"Alarm"},"glas":{"ln":"Glass"}};
  var isChristmas = 0;
  var newMap = 1;

And this is the code I had to write to parse it:

o = lambda do |x|
  next true if x == [:true]
  next x.size != 2 ? fail : eval(x[1].to_s) if x[0] == :lit || x[0] == :str
  next x.size != 2 ? fail : Hash[ x[1].map do |a,b,c|
    fail unless a == :property
    fail unless b.is_a? Symbol
    [eval(b.to_s).to_sym, o[c]]
  end ] if x.first == :object
  fail x.inspect
end

require "rkelly"

result = Hash[ RKelly::Parser.new.parse(my_js_code).to_sexp.map do |k, v|
  fail unless k == :var
  fail unless v.size == 1
  a, b, c = v.first
  fail unless a == :var_decl
  k, v = c
  fail unless k == :assign
  [b, o[v]]
end ]

That results in:

{:xpos=>0,
 :ypos=>0,
 :city=>"Parish",
 :cashSaldo=>"0.00",
 :bankSaldo=>"",
 :address=>"Lot: 0 - 0",
 :simplemode=>true,
 :email_reminder=>true,
 :text_citylist=>"Take a cab to",
 :text_nostreet=>"Lot",
 :text_lotpos=>"Lot:",
 :text_products_title=>"Products",
 :text_products_subtitle=>"Produce and set prices",
 :text_title=>"Miniconomy",
 :text_has_harbor=>"This city has a harbor",
 :products=>
  {:gron=>{:ln=>"Clay"},
   :stee=>{:ln=>"Brick"},
   :ijee=>{:ln=>"Iron Ore"},
   :boom=>{:ln=>"Tree"},
   :goud=>{:ln=>"Gold"},
   :olie=>{:ln=>"Oil"},
   :oven=>{:ln=>"Oven"},
   :ijze=>{:ln=>"Iron"},
   :hout=>{:ln=>"Wood"},
   :schi=>{:ln=>"Bulletproof Vest"},
   :benz=>{:ln=>"Gas"},
   :pomp=>{:ln=>"Pump"},
   :schr=>{:ln=>"Screwdriver"},
   :sche=>{:ln=>"Shovel"},
   :moto=>{:ln=>"Electrical Engine"},
   :plas=>{:ln=>"Plastic"},
   :zaag=>{:ln=>"Saw"},
   :mach=>{:ln=>"Machine"},
   :chip=>{:ln=>"Chip"},
   :tele=>{:ln=>"Telephone"},
   :came=>{:ln=>"Camera"},
   :alar=>{:ln=>"Alarm"},
   :glas=>{:ln=>"Glass"}},
 :isChristmas=>0,
 :newMap=>1}

Answer 3

You could use a regular expression to parse it out like this:

k = "function GetParam(name) { var req_var = { a: 'xyz' , b: 'yy.com' , c: 'en' , d:0 , e: 'y'}; }"
variable = k.match(/var\s+req_var\s+=\s+(.*?);/m)[1]
p variable

=> "{ a: 'xyz' , b: 'yy.com' , c: 'en' , d:0 , e: 'y'}"