javascript - setTimeout only sees last value in array?

I have an array of ids which I loop over and want to use in a function called by setTimeout, however when "func" below is executed it only seems to see the last id stored in the array.
I have been trying to uses closures to fix the issue but have had no success.

  // loop over array an call setTimeout for loading an image
  for (var i = 0; i < idlist.length; i++) {
    // variable i want use in function
    var lookup = idlist[i];


    var func = function() {
        alert(lookup); // this is always the last value in the "idlist" array
    };

    setTimeout(func, 500);
}