Get list of closure variables in Javascript


Are there any ability to get closure variables list (Ok, maybe all scope variables) in JavaScript?


function factory(){ var _secret = "Some secret"; return function(code){ // How to get parent function variables names here? // ... } } var inside = factory(); inside();


Assuming this is for debugging purposes, you can try parsing the function body and evaluating identifiers found:

<pre class="snippet-code-js lang-js prettyprint-override">function getvars(fn, _eval) { var words = String(fn).replace(/".*?"|'.*?'/g, '').match(/\b[_A-Za-z]\w*/g), ret = {} words.forEach(function(w) { try { ret[w] = _eval(w) } catch (e) {}; }); return ret; } function factory() { var _secret = "Some secret"; var _other = "Other secret"; return function(code){ var vars = getvars(factory, _ => eval(_)); return vars; } } vars = factory()(); document.write('<pre>'+JSON.stringify(vars,0,3));

Needless to say, this is an extremely naive way to deal with code, so handle it with care.


There's no comprehensive way to get a list of all variables in scope. You could enumerate over the this object, but that will still only give you a list of the <em>enumerable</em> objects on this, and even at that there will still be things like function arguments that aren't on this.

So no, this cannot be done. Also check out this <a href="https://stackoverflow.com/questions/2051678/getting-all-variables-in-scope" rel="nofollow">similar question</a>.


No, it isn't possible. ECMAScript specification doesn't expose <a href="http://www.ecma-international.org/ecma-262/6.0/#sec-environment-records" rel="nofollow">Enviroment Record</a> objects to end user anywhere.


Since the primary concept of a closure is scope, and vars inside a closure are private, there can be no way to achieve this without exposing them somehow, like via a method.

What are you really trying to achieve?


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