3 Random Numbers

[cluksha]

I am trying to pick 3 random numbers from an array length. (I have 5 images that I need to show 3 of each time a page loads - but none can be the same.)

So I need to pick 3 random images from a list of 5 and ther ecan be no duplicates - like I have already done in this post

Anyway I grabbed a script from somewhere I can't remember. and modified it slightly - but I keep getting "undefined" returned as a result.

If you try this code you will see what I mean...

//creates new array filled w/ images and new array filled w/ URL's
images = new Array("agility","strength","balance","power","speed")
//So you can add and subtract images as you choose w/o worry
imgCt = images.length


<!-- Begin
num= new Array(imgCt);
for (i in images) {

num=Math.round(imgCt*Math.random()+1);
if (num[1]==num[0]) {
while (num[1]==num[0]) {
num[1]=Math.round(imgCt*Math.random()+1);
}
}
if (num[2]==num[1] || num[2]==num[0]) {
while (num[2]==num[1] || num[2]==num[0]) {
num[2]=Math.round(imgCt*Math.random()+1);
}
}
if (num[3]==num[2] || num[3]==num[1] || num[3]==num[0]) {
while (num[3]==num[2] || num[3]==num[1] || num[3]==num[0]) {
num[3]=Math.round(imgCt*Math.random()+1);
}
}

document.write(images[num],"-",i,",");
//This is here for testing purposes only
}

Then I want to put this in the page -
document.write ("<a href='programs/'" + eval(images[num[0]]) + "><img src='img/" + eval(images[num[0]]) + ".jpg' width=750 height='122' border='0' alt=''></a><br>");


Can anyone help me find the solution here? ( I will be away fro a few days at this point but at least I have it out there for you to see.

Thanks so much,
Chris

Chris Luksha
Echo Web Services
Making Your Website Resound

http://www.echowebservices.com

 

[vongrunt]

This:

Math.round(imgCt*Math.random()+1);

... generates number between 1 and 6. You need between 0 and 4, right?

------
[small]select stuff(stuff(replicate('<P> <B> ', 14), 109, 0, '<.'), 112, 0, '/')[/small]

 

[cluksha]

That line actually generates number from 0-4 as there are 5 items in my imgCt var. The problem is that occassionally it generates an "undefined" when pulling it's relative item from the images array.

So if the value is undefined - then it will not show an image.

Thanks
Chris

Chris Luksha
Echo Web Services
Making Your Website Resound

http://www.echowebservices.com

 

[tsuji]

As said, the formula for generating num before testing is not correct. This is how you can do it more neatly and easier to read.
[tt]
for (var i=0;i<num.length;i++) {
do {
var b=true;
num=Math.floor(imgCt*Math.random());
for (var j=0;j<i;j++) {
if (num[j]==num) { b=false; break;}
}
} while (!b)
}
alert(num); //just to show
[/tt]

 

[trollacious]

It's generating the "undefined" because you're rounding the random number, then adding one. That could result in an index number 2 greater than the length of the array.

Try the following code. It should be flexible enough for your requirements.

<script language="javascript" type="text/javascript">

var pics = new Array(), numpics = 4;
var img = new Array("agility","strength","balance","power","speed");
var imglength = img.length;

for (var pi=0;pi<numpics;pi++)
  {
  do
    {
    var duplicate = false;
    pics[pi] = Math.floor(Math.random() * imglength);
    for (var ni=0;ni<pi;ni++)
      {
      if (pics[pi] == pics[ni])
        {
        duplicate = true;
        }
      }
    }
  while (duplicate == true);
  
  //display the image name chosen randomly.
  alert(img[pics[pi]]);
  }
</script>

Lee