Prevent access to Document and Window objects

no_W_no_D.js

// http://jsbin.com/igonuh/1/edit

function Fx(){return function(){return -1;};}
function SafeThis(that){ 
    if (that == window) {
        return fakeWindow;
    } else if (that == document) {
        return fakeDocument;                    
    } else {
        return that;
    }
}
var fakeDocument = {
    write: function(a){ document.write(a + "<br>"); }
};
var fakeWindow = {
    document: fakeDocument
};
 
var moduleA = function(Function, window, document, eval){
    var f = new Function("return this");
    document.write(f());
 
    var win = (function(){return this;})();
    document.write(win);
 
    var set = (function(){this.a = 1;return this.a})();
    document.write(set);
 
    var e = eval("this"); 
    document.write(e);
 
    document.write(this);
    document.write(window);
    document.write(document);
 
    this.a = 1;
    document.write(JSON.stringify(this));
};
 
var moduleA_Fx = '!' + 
    moduleA.toString().replace(/\bthis\b/g,"SafeThis(this)") + 
    '(Fx,fakeWindow,fakeDocument,Fx)';
 
document.write(moduleA_Fx + "<br><br>");
 
eval(moduleA_Fx);
 
document.write(this.a);