Function.toString() not respecting closure scope

Question

Function.toString() not respecting closure scope

var foo = (function(){
  var x = "bar";
  return function(){
    console.log(x);
  };
})();

console.log(foo.toString()); // function() {console.log(x);}

(foo)(); // 'bar'
eval('(' + foo.toString()+')()')); // error: x is undefined

Why isn't the var x recorded as "bar" in foo.toString()?

foo has a behavior that does not match its toString() value. foo always prints "bar", but looking at foo.toString() would not tell you this.

Is it related to this? If a decision was made not to decompile a function to get its toString() value, why not include the resolution of objects which rely on an external function's scope?

Is there a way to use the old method of decompilation to get the actual code behind a given function?

javascript
node.js

Answer 1

You are executing the anonymous function, so the return value is assigned to foo. If you use

var foo = function(){
  var x = "bar";
  return function(){
    console.log(x);
  };
};

foo.toString() shows the anonymous function and
foo().toString() the returned function

Your eval creates a new function from foo.toString()¹, not in any way related to the scope of the initial scope [of the anonymous function that created foo], and executes that, so it results in a ReferenceError concerning x. There's nothing strange about that.

¹ eval("function (){console.log(x);})()")