Help with multiple random images

[sg123]

Here's the code I slightly modified from the source found on javascriptkit.com:

<script>
function random_imglink(){
  var myimages = new Array()
    myimages[1] = "01.jpg"
    myimages[2] = "02.jpg"
    myimages[3] = "03.jpg"
    myimages[4] = "04.jpg"
    myimages[5] = "05.jpg"
    ...
    myimages[31] = "31.jpg"
							
  var rq=Math.floor(Math.random()*myimages.length)
  var rr=Math.floor(Math.random()*myimages.length)
  var rs=Math.floor(Math.random()*myimages.length)
  var rt=Math.floor(Math.random()*myimages.length)
  var ru=Math.floor(Math.random()*myimages.length)
  var rv=Math.floor(Math.random()*myimages.length)
  var rw=Math.floor(Math.random()*myimages.length)
  var rx=Math.floor(Math.random()*myimages.length)
  var ry=Math.floor(Math.random()*myimages.length)
  var rz=Math.floor(Math.random()*myimages.length)

  if (ry==0)
    ry=1
    document.write('<img src="'+myimages[rq]+'"> &nbsp;<img src="'+myimages[rr]+'"><br><img src="'+myimages[rs]+'"> &nbsp;<img src="'+myimages[rt]+'"><br><img src="'+myimages[ru]+'"> &nbsp;<img src="'+myimages[rv]+'"><br><img src="'+myimages[rw]+'"> &nbsp;<img src="'+myimages[rx]+'"><br><img src="'+myimages[ry]+'"> &nbsp;<img src="'+myimages[rz]+'">')
}
random_imglink()
</script>

I have 8 IMGs grabbing images randomly from a list of 31 JPGs & here's my dilemma:
1. I don't want the same image appearing in more than 1 spot
2. When I test this, sometimes 1 or more IMG spots return an undefined image

Any help would be greatly appreciated. Thanks in advance!

[felgall]

Shuffle the arrat and then grab as many as you need off the front.

Array.prototype.shuffle = function() {
   var s = [];
   while (this.length) s.push(this.splice(Math.random() * this.length, 1)[0]);
   while (s.length) this.push(s.pop());
   return this;
}; 

function random_imglink(){
  var myimages = []
    myimages[1] = "01.jpg"
    myimages[2] = "02.jpg"
    myimages[3] = "03.jpg"
    myimages[4] = "04.jpg"
    myimages[5] = "05.jpg"
    ...
    myimages[31] = "31.jpg"

myimages.shuffle();
   
    var rq = myimages[0];
    var rr = myimages[1];
// ... etc

[sg123]

That worked perfectly!

Here's the fixed code block in case someone else is looking for the same solution:

Array.prototype.shuffle = function(){
	var s = [];
	while (this.length) s.push(this.splice(Math.random() * this.length, 1)[0]);
	while (s.length) this.push(s.pop());
	return this;
};
function random_imglink(){
	var myimages = []
		myimages[0] = "01.jpg"
		myimages[1] = "02.jpg"
		myimages[2] = "03.jpg"
		myimages[3] = "04.jpg"
                ...
		myimages[30] = "31.jpg"

		myimages.shuffle();

		var rq = myimages[0];
		var rr = myimages[1];
		var rs = myimages[2];
                ...
		var rz = myimages[9];

	document.write('<img src="images/thumbnails/'+rq+'"> &nbsp;<img src="images/thumbnails/'+rr+'"><br><img src="images/thumbnails/'+rs+'"> &nbsp;<img src="images/thumbnails/'+rt+'"><br><img src="images/thumbnails/'+ru+'"> &nbsp;<img src="images/thumbnails/'+rv+'"><br><img src="images/thumbnails/'+rw+'"> &nbsp;<img src="images/thumbnails/'+rx+'"><br><img src="images/thumbnails/'+ry+'"> &nbsp;<img src="images/thumbnails/'+rz+'">')
}
random_imglink()