Say I have this function:
function test(){
return a + b + 1;
}
How can I dynamically figure out that it will require globals a and b to be able to run? E.g. something like get_dependencies(test) returns ['a', 'b']
2 Answers
There's no built-in way to do that in standard JavaScript, if you're trying to do it with JavaScript itself.
On nearly all (but not all) JavaScript engines, you can get a form of the source of a function from the function object's toString function, e.g.:
var testSource = test.toString();
...and then of course you could parse that. This is non-standard behavior (the result of calling toString on a function is not defined in the specification), but it's widely-supported. You'd still have to do the parsing to find the symbols.
For the parsing, you have a couple of options. You could try to separate the parser portion of JSLint out of the rest of it, or alternately the terribly-named UglifyJS compressor has a full JavaScript parser which is already separate from the compressor part (see parse-js.js; apparently there's a tiny bit of NodeJS-specific stuff you might want to remove).
3 Comments
Trindaz
Thanks @T.J. I might give this a try - I'm guessing there's a regex that's not too complicated that would cover 90% of cases which is good enough for me for now.
T.J. Crowder
@Trindaz: Re the regex: Probably not. Consider the complexity of comments (both styles of them), string literals (both styles of them), regular expression literals, etc. A simple regex giving you, for instance, all of the identifier-like things would be blown up by those. Still, with some pre-processing you could probably do a 90% solution...
T.J. Crowder
@Trindaz: Added some notes to the answer on parsing.
You can use a Javascript 'lint' tool that will test your code for common mistakes or oddities.
Some can be found online:
- http://www.jslint.com/
- http://www.javascriptlint.com/online_lint.php (can also be downloaded)
In your case, you might want to isolate individual functions via a regular expression for example, and submit them to such a tool.
aandbdon't have to be globals, they just have to be defined in the containing scope (which may not be the global scope).