Example of how to eval and then eval some more, adding to the scope of the first eval.

evaluator.js

var evaluatorString =
'(function(stuff) {'+
  ' return eval("(function() {"'+
                   '+stuff+'+
                   '"return "+evaluatorString+";'+
                 '})();");'+
 '})';
var scope1 = eval(evaluatorString);
var scope2 = scope1('var myVar = 42;');
var scope3 = scope2('console.log(myVar); myVar = myVar * 2;');
scope3("console.log(myVar);");