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I wanted to be able to get a list of all variables in the current scope. I know it may not be possible (ex. 1, 2, 3 but it would really be helpful in simplifying a parsing algorithm for a Node/browser library I'm currently working on.

One thing: it doesn't need to be printed or safe from 'minification'.

I was wanting to be able to figure out what variables were introduced by reading a JS library and dynamically evaling it, finding the difference in state between the two. I know this approach sounds terrible on paper (I'm well acquainted with the hatred of eval), but if there is a better way to find this than just simply parsing the whole library (which is slow for any language other than C/etc.), I'm all ears.

For you all right off crying over the blatant use of eval, I know to use closures to protect the parent scope from modification. I also will be able to prevent changes to the browser display in the eval as well if it is in a browser environment (temporarily change some DOM constructors).

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Claudia
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  • Sounds like you wanted to use a proper IDE… – Bergi May 12 '14 at 22:56
  • It has to do with the application I'm currently developing, a JS compiler with both Node and the browser being targets. Maybe that should give a little background. Also, I am fully aware that those kinds exist, but I'm looking to something that would be a little more fully featured in the sense of being more like GCC for JS than just a simple obfuscator. UglifyJS2 and the Closure Compiler are both seeming to poorly optimize several things IMO, and require separate tools to build and minify, which makes little sense. – Claudia May 13 '14 at 15:21
  • So you mean you're actually dealing with the syntax tree of the to-be-transpiled javascript? You would need to make that more clear, everybody assumes that you're executing code and want to programmatically access scope. – Bergi May 13 '14 at 15:25
  • Not necessarily. What everyone assumes is pretty much correct, but I'm about to post my own answer here (for what I was basically looking for). – Claudia May 13 '14 at 15:38
  • Well, if you're using `eval` and actually are executing (sideeffectful) code *in a transpiler*, then I *am* crying indeed. – Bergi May 13 '14 at 15:41
  • I would obviously be running it with plenty of precautions (such as rewriting DOM constructors to no-op equivalents) – Claudia May 13 '14 at 15:46
  • Either way, I'm going to close this question...I've found a decent and fast parser that I could use to avoid the mess (I've helped it along a little). – Claudia May 13 '14 at 15:47
  • Actually, my *potential* answer didn't work. – Claudia May 13 '14 at 16:08

1 Answers1

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Yes and no. "No" in almost every situation. "Yes," but only in a limited manner, if you want to check the global scope. Take the following example:

var a = 1, b = 2, c = 3;

for ( var i in window ) {
    console.log(i, typeof window[i], window[i]);
}

Which outputs, amongst 150+ other things, the following:

getInterface function getInterface()
i string i // <- there it is!
c number 3
b number 2
a number 1 // <- and another
_firebug object Object firebug=1.4.5 element=div#_firebugConsole
"Firebug command line does not support '$0'"
"Firebug command line does not support '$1'"
_FirebugCommandLine object Object
hasDuplicate boolean false

So it is possible to list some variables in the current scope, but it is not reliable, succinct, efficient, or easily accessible.

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