Javascript automatic next image

I created this site which uses a simple javascript function to show images based on the user mousing over or clicking numbered boxes on the right. Now after testing it's been determined that 开发者_Python百科an automatic slideshow should be added on top of this, so that next image will show after a few seconds.

http://www.philippedollo.com/photo/fineart/f_amw.htm

Is there a way to amend this code easily to make it happen easily? --

function showPic(whichpic) {
    if (document.getElementById) {
        document.getElementById('placeholder').src = whichpic.href;
        if (whichpic.title) {
            document.getElementById('desc').childNodes[0].nodeValue = whichpic.title;
        } else {
            document.getElementById('desc').childNodes[0].nodeValue = whichpic.childNodes[0].nodeValue;
        }
        return false;
    } else {
        return true;
    }
}

Use setInterval().

function getNextPic()
{
    // ???
}

setInterval(function ()
{
    showPic(getNextPic());
}, 3000); // 3 seconds

There's no need for the if(document.getElementById) check, since the function is 100% cross-browser.

function showPic(whichpic)
{
    document.getElementById('placeholder').src = whichpic.href;

    document.getElementById('desc').childNodes[0].nodeValue = whichpic.title ?
        whichpic.title : whichpic.childNodes[0].nodeValue;

    return false;
}

The following should work for you, I tested it and it works fine on my end.

var curPic,
    gallery,
    pics;

function cyclePic(){
    if(curPic < pics.length){
        showPic(pics[curPic]);
    }
    curPic++;
    setTimeout(cyclePic,5000);
}

function showPic (whichpic) {
     if (document.getElementById) {
      document.getElementById('placeholder').src = whichpic.href;
      if (whichpic.title) {
       document.getElementById('desc').childNodes[0].nodeValue = whichpic.title;
      } else {
       document.getElementById('desc').childNodes[0].nodeValue = whichpic.childNodes[0].nodeValue;
      }
      return false;
     } else {
      return true;
     }
}

window.onload = function(){
    curPic = 0,
    gallery = document.getElementById("gallery"),
    pics = gallery.getElementsByTagName("a");
    cyclePic();
}