How to Rotate/Slideshow Text DIVs on page?

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I am trying to modify the script below to slideshow/rotate through a handful of text DIVs.

I need these DIVs to appear in order-- div 1, then div 2, then div 3. Each would appear for 5 seconds, then show the next div... but in order.

The script below works well for Random divs, but I need them to be in order-- div 1, div 2, div 3... each time.

<div id="d1" style="display:none;">some text 1</div>
<div id="d2" style="display:none;">some text 2</div>
<div id="d3" style="display:none;">some text 3</div>

<script type="text/javascript">
divs = ['d1','d2','d3'];

function hideDivs() {
for (var i=0; i<divs.length; i++)
document.getElementById(divs[i]).style.display = 'none';
}

function showDiv() {
hideDivs(); //hide them all before we show the next one.
var randomDiv = divs[Math.floor(Math.random()*divs.length)];
var div = document.getElementById(randomDiv).style.display =
'block';

setTimeout(showDiv,500); //set a delay before showing the next div
}

showDiv();
</script>