JavaScript Function Isolation

gist.js

var root=this;

function getIsolationScript(){
  //getting key of global attrs
  var buffer="";
  for(var x in root)buffer+="try{var "+x+"=void 0}catch(e){}";
  //the name of the top-level variable
  // should be manually set.
  buffer+="var window={}";
  return buffer;
}

function isolate(){
  eval(getIsolationScript());
  //
  //we are in the sandbox!
  //
}