Difference between window[] and eval() - Javascript

Question

I've been using both in javascript ... really don't know the difference. Googling always shows results for the "window object" or "opening a new window in javascript" so couldn't find anything there.

 eval("v"+e)
 window["v"+e]

Sometimes window works for me and at other times eval works ....

So what's the difference between eval() and window[] ?

Sorry for the newbie question though !

Norman

Answer 1

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.

Answer 2

eval() interprets arbitrary javascript statements, whereas with window you are accessing a property of the window object.

In your example, you seem to be using a property name in both eval() and window[]. As the global scope in a browser is the same as the window object's scope they will evaluate to the same thing.

You can think of your eval("v"+e) statement as being equivalent to eval("window['v'" + e +" ]").