extracting strings from JavaScript code

Question

Using embedded SpiderMonkey in my C++ application I would like to extract all the strings from JavaScript code. JavaScript code looks something like this:

var foo = "something";  
var space = " ";  
var bar = foo + space + "beautiful";

C++ code looks like this:

char *script = "var foo = \"something\"; var space = \" \"; var bar = foo + space + \"beautiful\";";
ok = JS_EvaluateScript(cx, global, script, strlen(script), filename, lineno, &rval);

So my questions is, after SpiderMonkey executes JavaScript, how can I extract the string from variable bar (extracted value should be "something beautiful") and use it in my regular C++ code? I guess I have to evaluate the script first and then somehow extract the string from the JavaScript variable. I don't know how to extract the string using SpiderMonkey.

My second question:
http://siliconforks.com/doc/parsing-javascript-with-spidermonkey/
This SpiderMonkey JavaScript parser is written for SpiderMonkey 1.6. How can this be done with latest SpiderMonkey, because APIs for parsing have changed?

Thnx in advance,
Goran

Please be more clear on the context in which you need to extract. If you are talking about passing content of client-side JS variables to server side C++ you need to send the vars to the server using http (ajax, form) — mplungjan, Aug 31 '11 at 08:50
@mplungjan I wasn't very precise. I have embedded SpiderMonkey in my C++ app. Short snippet: char *script = "var foo = 'some string'"; ok = JS_EvaluateScript(cx, global, script, strlen(script), filename, lineno, &rval); How can I now get to the value of JavaScript variable foo? — Goran, Aug 31 '11 at 09:12
@mplungjan Updated. Do You know to solve my problem? Maybe You can give me some directions so I can investigate further? Thank You. — Goran, Aug 31 '11 at 11:51
I think this is a duplicate http://stackoverflow.com/questions/639514/how-can-i-get-the-memory-address-of-a-javascript-variable More here: http://stackoverflow.com/search?q=spidermonkey+[c%2B%2B]+javascript+variable&submit=search I have no idea myself — mplungjan, Aug 31 '11 at 14:22

score 0 · Accepted Answer · answered Aug 31 '11 at 16:41

0

Since bar is property of global object, after the JS_EvaluateScript() I can use JS_GetProperty() function, something like this

JS_GetProperty(cx, global, "bar", &rval);
JSString *str = JS_ValueToString(cx, rval);
printf("%s\n", JS_EncodeString(cx, str));

answered Aug 31 '11 at 16:41

Goran

143
2
7

The above example NO LONGER WORKS with the latest Mozilla JavaScript version 38 or newer (both `js` and `xpcshell`) – John Greene May 23 '16 at 20:08

score -1 · Answer 2 · answered Aug 31 '11 at 08:45

-1

Check String operation functions like subString. It can be used to resolve your query.

answered Aug 31 '11 at 08:45

Umesh Patil

10,475
16
52
80

substring. Not subString - and I doubt that is what he needs. – mplungjan Aug 31 '11 at 08:47

extracting strings from JavaScript code

2 Answers2