How to randomize fadeTo?

This is a tiny js file, grabbed from somewhere, used in wordpress to make thumbnails fade in on page load.

(function($) {
    $('.featured-thumbnail').each(function(i) {
        $(this).delay((i++) * 380).fadeTo(1000, 1); })
})(jQuery);

I'd like to add randomness to i.

The questions are: Where to use Math.random? Should I use Math.floor also? Do I need total i? Doesn't appear to be necessary.

Slow learning jQuery newbie.

Sounds like you want the thumbnails fading-in in a random order. If you're OK with those fade-ins overlapping, you can say:

(function($) {
    var len = $('.featured-thumbnail').length;

    $('.featured-thumbnail').each(function(i) {
    $(this).delay(Math.floor( Math.random() * 380 * len)).fadeTo(1000, 1); })
})(jQuery);

otherwise, you can pick off random elements off your list and fade them in on the same schedule as the original:

(function($) {
  // jQuery selectors return array-LIKE objects,
  // but not actual arrays. We need a real array.
  //
  var items = $.makeArray( $('.featured-thumbnail') );
  var i = 0;

  while (items.length > 0)
  {
    // pick a random index within our array
    //
    var idx = Math.floor( Math.random() * items.length );

    // grab that item, remove it from the array.
    // splice() returns an array, so grab the first (only)
    // element from that array. splice() removes the
    // selected element(s) from the original array
    //
    var selected = items.splice(idx, 1)[0]; 

    // delay and fade in as before
    //
    $(selected).delay(i++ * 380).fadeTo(1000, 1);
  }
})(jQuery);