Another point that has not been addressed is that eval will resolve the variable reference using the caller variable environment, for example:

var foo = global;



(function () {

  var foo = local;

  alert(eval(foo)); // alerts local

  alert(window[foo]); // alerts global

})();

So as you can see, is not completely equivalent.

If you simply want to reference a global variable, I would recommend you to use the window[prop] approach and avoid surprises.