random text script, BUT no repeating

[Jennie Friesen]

Hello--

I would like to display a different line of text (32 different
messages) on refresh, BUT with no repeats.

The script I am currently using is:

<script language=javasc ript type=text/javascript>
<!--
a = Math.floor(Math .random() * 32);
switch (a){
case 0 :
document.write( "msg 1 here");
break;
case 1 :
document.write( "msg 2 here");
break;
}
// etc., up to 32 cases
//-->
</script>

I notice that many random text scripts use an array to store the text
messages, and was thinking that incorporating a line in the script
where the array value that was most recently accessed would be
deleted, would make its subsequent selection impossible, thereby
solving the no-repeats.

In the script below, can one suggest where the delete line would fit
in and what its syntax would be?

thank you in advance!
JF

<SCRIPT LANGUAGE="Javas cript">
// <!--
function text() {
};

text = new text();
number = 0;

// textArray
text[number++] = "Random text string 1."
text[number++] = "Random text string 2."
text[number++] = "Random text string 3."
text[number++] = "Random text string 4."
text[number++] = "Random text string 5."
// keep adding items here...

increment = Math.floor(Math .random() * number);

document.write( text[increment]);

// where does delete text[number++] fit in?

//--></SCRIPT>

[Dan Brussee]

Re: random text script, BUT no repeating

In article <bef3c3af.03062 91642.25211147@ posting.google. com>,
jenniefriesen@y ahoo.ca says...[color=blue]
> Hello--
>
> I would like to display a different line of text (32 different
> messages) on refresh, BUT with no repeats.[/color]

Think of this is a sort of card shuffling routine. You have 32 cards and
want them randomized. Obviously, not duplicates.

A common way of doing this in gaming is to take the array of cards and
just mix up their values. Then go through the array one at a time as if
they were NOT shuffled. Psuedo-code follows:

var a;
var b;
var tmp;
for (var y = 0; y < 10; y++) { // repeat shuffle y times
for (var x = 0; x < 32; x++) {
a = math.random(32) ; // cant remember the method here... sorry.
b = math.random(32) ;
tmp = ary(a);
ary(a) = ary(b);
ary(b) = tmp;
}
}

for (var x = 0; x < 32; x++) {
document.write( "Item " + x + ": " + ary(x) + "<br/>");
}

--

Remove NOT from email address to reply. AntiSpam in action.

[Tim Williams]

Re: random text script, BUT no repeating

You want to do this every time the page is refreshed?
Unless this is a framed page, it's not clear how the page will know what the
last-used line was...

tim.




"Jennie Friesen" <jenniefriesen@ yahoo.ca> wrote in message
news:bef3c3af.0 306291642.25211 147@posting.goo gle.com...[color=blue]
> Hello--
>
> I would like to display a different line of text (32 different
> messages) on refresh, BUT with no repeats.
>
> The script I am currently using is:
>
> <script language=javasc ript type=text/javascript>
> <!--
> a = Math.floor(Math .random() * 32);
> switch (a){
> case 0 :
> document.write( "msg 1 here");
> break;
> case 1 :
> document.write( "msg 2 here");
> break;
> }
> // etc., up to 32 cases
> //-->
> </script>
>
> I notice that many random text scripts use an array to store the text
> messages, and was thinking that incorporating a line in the script
> where the array value that was most recently accessed would be
> deleted, would make its subsequent selection impossible, thereby
> solving the no-repeats.
>
> In the script below, can one suggest where the delete line would fit
> in and what its syntax would be?
>
> thank you in advance!
> JF
>
> <SCRIPT LANGUAGE="Javas cript">
> // <!--
> function text() {
> };
>
> text = new text();
> number = 0;
>
> // textArray
> text[number++] = "Random text string 1."
> text[number++] = "Random text string 2."
> text[number++] = "Random text string 3."
> text[number++] = "Random text string 4."
> text[number++] = "Random text string 5."
> // keep adding items here...
>
> increment = Math.floor(Math .random() * number);
>
> document.write( text[increment]);
>
> // where does delete text[number++] fit in?
>
> //--></SCRIPT>[/color]

[Dr John Stockton]

Re: random text script, BUT no repeating

JRS: In article <MPG.1969572b7c 91c646989781@ne ws-server.nc.rr.co m>,
seen in news:comp.lang. javascript, Dan Brussee <dbrussee@NOTbe tterwaycom
puting.com> posted at Mon, 30 Jun 2003 01:06:41 :-[color=blue]
>In article <bef3c3af.03062 91642.25211147@ posting.google. com>,
>jenniefriesen@ yahoo.ca says...[color=green]
>> Hello--
>>
>> I would like to display a different line of text (32 different
>> messages) on refresh, BUT with no repeats.[/color]
>
>Think of this is a sort of card shuffling routine. You have 32 cards and
>want them randomized. Obviously, not duplicates.
>
>A common way of doing this in gaming is to take the array of cards and
>just mix up their values. Then go through the array one at a time as if
>they were NOT shuffled. Psuedo-code follows:
>
>var a;
>var b;
>var tmp;
>for (var y = 0; y < 10; y++) { // repeat shuffle y times
> for (var x = 0; x < 32; x++) {
> a = math.random(32) ; // cant remember the method here... sorry.
> b = math.random(32) ;
> tmp = ary(a);
> ary(a) = ary(b);
> ary(b) = tmp;
> }
>}
>
>for (var x = 0; x < 32; x++) {
> document.write( "Item " + x + ": " + ary(x) + "<br/>");
>}[/color]

Pseudo.

Good idea, bad algorithm. See FAQ 4.22, both for
function Random(x) { return Math.floor(x*Ma th.random()) }
// generates random integer in 0 .. x-1
and for a link to efficient dealing and shuffling.

For N items, there are N! possible orders, so for a good shuffle the
operation must have [a multiple of] N! possible outcomes, all equi-
probable. For this it is both necessary and sufficient to call
Random(N) ... Random(2 or 1).

With, therefore, a little subtlety in your x loop, the y loop is not
needed.

function Shuffle(Q) { var R, T, J
for (J=Q.length-1 ; J>0 ; J--)
{ R=Random(J+1) ; T=Q[J] ; Q[J]=Q[R] ; Q[R]=T }
return Q }

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 MSIE 4 ©
<URL:http://jibbering.com/faq/> Jim Ley's FAQ for news:comp.lang. javascript
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