On: -= sequoia capital =-

[invisible]

That's actually way slower because you're doing a comparison within an iteration. That's putting an if statement inside a loop while the result is the same for every iteration.

[ars → invisible]

Computers are not that slow these days :)

It reduces complexity and a global, which is far more important.

And that blink loop is probably not that big - just how many blink tags do you have?

I don't use it for blink loops anyway, I use it for toggle on/off, where keeping state for each element individually is pretty important.

[invisible → ars]

You're accessing the DOM every iteration, so I'd bet that it does matter somewhat if blink is used a lot.

You can avoid polluting by make it an actual function and then setting the function.blinkOn instead.

You're right: individually swapping them this works better, but the intent is to have them all off or all on.

  (function() {
    var blinkIterator = function() {
        var blinks = document.getElementsByTagName("blink"),
         onOff = blinkIterator.blinkOn ? "" : "hidden";
        for (var i = 0, l = blinks.length; i < l;)
            blinks[i++].style.visibility = onOff;
        blinkIterator.blinkOn ^= 1;
    };
    blinkIterator.blinkOn = 1;
    window.setInterval(blinkIterator, 750);
  })();