randomize array - Javascript

Jeff Thies

I'd like to randomly sort an array. A good method?

Jul 23 '05 #1

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4166

Nik Coughin

Jeff Thies wrote:

I'd like to randomly sort an array. A good method?

Untested (but modified from a working script):

function Random( low, high )
{
with( Math )
{
return floor(random() * ( 1 + high - low ) + low );
}
}

var unSorted = new Array( 5 );
var Sorted = new Array( 5 );
var used = new Array( 5 );

unSorted[ 1 ] = '<a href="one.html" >One</a>';
unSorted[ 2 ] = '<a href="two.html" >Two</a>';
unSorted[ 3 ] = '<a href="three.htm l">Three</a>';
unSorted[ 4 ] = '<a href="four.html ">Four</a>';
unSorted[ 5 ] = '<a href="five.html ">Five</a>';

for( ii=1; ii<=5; ii++ )
{
Used[ ii ] = false;
}

for( ii=1; ii<=5; ii++ )
{
randomNumber = Random( 1, 5 );
while( used[ randomNumber ] )
{
randomNumber = Random( 1, 5 );
}
sorted[ ii ] = inSorted[ randomNumber ];
used[ randomNumber ] = true;
}

Jul 23 '05 #2

Nik Coughin

Nik Coughin wrote:

Jeff Thies wrote:
I'd like to randomly sort an array. A good method?
Untested (but modified from a working script):

function Random( low, high )
{
with( Math )
{
return floor(random() * ( 1 + high - low ) + low );
}
}

var unSorted = new Array( 5 );
var Sorted = new Array( 5 );
var used = new Array( 5 );

unSorted[ 1 ] = '<a href="one.html" >One</a>';
unSorted[ 2 ] = '<a href="two.html" >Two</a>';
unSorted[ 3 ] = '<a href="three.htm l">Three</a>';
unSorted[ 4 ] = '<a href="four.html ">Four</a>';
unSorted[ 5 ] = '<a href="five.html ">Five</a>';

for( ii=1; ii<=5; ii++ )
{
Used[ ii ] = false;
}

for( ii=1; ii<=5; ii++ )
{
randomNumber = Random( 1, 5 );
while( used[ randomNumber ] )
{
randomNumber = Random( 1, 5 );
}
sorted[ ii ] = inSorted[ randomNumber ];

Above line should read:

sorted[ ii ] = unSorted[ randomNumber ];
used[ randomNumber ] = true;
}

Jul 23 '05 #3

Nik Coughin

Nik Coughin wrote:

Jeff Thies wrote:
I'd like to randomly sort an array. A good method?
Untested (but modified from a working script):

function Random( low, high )
{
with( Math )
{
return floor(random() * ( 1 + high - low ) + low );
}
}

var unSorted = new Array( 5 );
var Sorted = new Array( 5 );
var used = new Array( 5 );

unSorted[ 1 ] = '<a href="one.html" >One</a>';
unSorted[ 2 ] = '<a href="two.html" >Two</a>';
unSorted[ 3 ] = '<a href="three.htm l">Three</a>';
unSorted[ 4 ] = '<a href="four.html ">Four</a>';
unSorted[ 5 ] = '<a href="five.html ">Five</a>';

for( ii=1; ii<=5; ii++ )
{
Used[ ii ] = false;

Sorry, another typo. Should be:

used[ ii ] = false;
}

for( ii=1; ii<=5; ii++ )
{
randomNumber = Random( 1, 5 );
while( used[ randomNumber ] )
{
randomNumber = Random( 1, 5 );
}
sorted[ ii ] = inSorted[ randomNumber ];
used[ randomNumber ] = true;
}

Jul 23 '05 #4

Nik Coughin

Jeff Thies wrote:

I'd like to randomly sort an array. A good method?

Ignore my previous posts. Didn't test it and it didn't work. Think it had
too many capitalisation related errors. This works:

<html>
<head>
<title>Test</title>
</head>
<body>
<script language="JavaS cript" type="text/javascript">
function Random( low, high )
{
with( Math )
{
return floor(random() * ( 1 + high - low ) + low );
}
}

var unSorted = new Array( 5 );
var Sorted = new Array( 5 );
var used = new Array( 5 );

unSorted[ 1 ] = '<a href="one.html" >One</a>';
unSorted[ 2 ] = '<a href="two.html" >Two</a>';
unSorted[ 3 ] = '<a href="three.htm l">Three</a>';
unSorted[ 4 ] = '<a href="four.html ">Four</a>';
unSorted[ 5 ] = '<a href="five.html ">Five</a>';

for( ii=1; ii<=5; ii++ )
{
used[ ii ] = false;
}

for( ii=1; ii<=5; ii++ )
{
randomNumber = Random( 1, 5 );
while( used[ randomNumber ] )
{
randomNumber = Random( 1, 5 );
}
Sorted[ ii ] = unSorted[ randomNumber ];
used[ randomNumber ] = true;
}
</script>
</body>
</html>

Jul 23 '05 #5

Jeff Thies

> Jeff Thies wrote:

I'd like to randomly sort an array. A good method?
Ignore my previous posts. Didn't test it and it didn't work. Think it

had too many capitalisation related errors. This works:
Thanks Nik. It's better than what I might have thought up!

Curious about the length initializations : var used = new Array( 5 ); Does
that save resources, or is there another reason?

Cheers,
Jeff

<html>
<head>
<title>Test</title>
</head>
<body>
<script language="JavaS cript" type="text/javascript">
function Random( low, high )
{
with( Math )
{
return floor(random() * ( 1 + high - low ) + low );
}
}

var unSorted = new Array( 5 );
var Sorted = new Array( 5 );
var used = new Array( 5 );

unSorted[ 1 ] = '<a href="one.html" >One</a>';
unSorted[ 2 ] = '<a href="two.html" >Two</a>';
unSorted[ 3 ] = '<a href="three.htm l">Three</a>';
unSorted[ 4 ] = '<a href="four.html ">Four</a>';
unSorted[ 5 ] = '<a href="five.html ">Five</a>';

for( ii=1; ii<=5; ii++ )
{
used[ ii ] = false;
}

for( ii=1; ii<=5; ii++ )
{
randomNumber = Random( 1, 5 );
while( used[ randomNumber ] )
{
randomNumber = Random( 1, 5 );
}
Sorted[ ii ] = unSorted[ randomNumber ];
used[ randomNumber ] = true;
}
</script>
</body>
</html>

Jul 23 '05 #6

Nik Coughin

Jeff Thies wrote:

Jeff Thies wrote:
I'd like to randomly sort an array. A good method?

Ignore my previous posts. Didn't test it and it didn't work. Think
it had too many capitalisation related errors. This works:

Thanks Nik. It's better than what I might have thought up!

Curious about the length initializations : var used = new Array( 5 );
Does that save resources, or is there another reason?

To be honest, I don't know if it saves resources or even if it's necessary.
I don't know all that much about JavaScript, just the basic syntax. I'm
just lucky that it's similar enough to other languages that I've used that
pretty much everything I write works first time (except when I type
something out quickly and sloppily and fuck up the capitalisation) . I've
written in a lot of different languages (BASIC, Pascal, COBOL [yuck], c/c++,
vb, DarkBASIC, delphi, JavaScript, *nix shell, etc. etc. etc.), and I've
gotten into the habit of declaring arrays before I use them.

Jul 23 '05 #7

Nik Coughin

Nik Coughin wrote:

Jeff Thies wrote:
Jeff Thies wrote:
I'd like to randomly sort an array. A good method?

Ignore my previous posts. Didn't test it and it didn't work. Think
it had too many capitalisation related errors. This works:

Thanks Nik. It's better than what I might have thought up!

Curious about the length initializations : var used = new Array( 5 );
Does that save resources, or is there another reason?

To be honest, I don't know if it saves resources or even if it's
necessary. I don't know all that much about JavaScript, just the
basic syntax. I'm just lucky that it's similar enough to other
languages that I've used that pretty much everything I write works
first time (except when I type something out quickly and sloppily and
fuck up the capitalisation) . I've written in a lot of different
languages (BASIC, Pascal, COBOL [yuck], c/c++, vb, DarkBASIC, delphi,
JavaScript, *nix shell, etc. etc. etc.), and I've gotten into the
habit of declaring arrays before I use them.

That said, looking through the Wrox JavaScript Programmer's Reference, it
seems that they either need to be or should be declared.

Jul 23 '05 #8

Evertjan.

Nik Coughin wrote:

Jeff Thies wrote:
I'd like to randomly sort an array.

I would prefer randomizing by record swapping:
<script type="text/javascript">

var unSorted = new Array( 5 );
var randomlist = new Array( 5 );

unSorted[ 1 ] = '<a href="one.html" >One</a>';
unSorted[ 2 ] = '<a href="two.html" >Two</a>';
unSorted[ 3 ] = '<a href="three.htm l">Three</a>';
unSorted[ 4 ] = '<a href="four.html ">Four</a>';
unSorted[ 5 ] = '<a href="five.html ">Five</a>';

// random number generation
function Random( low, high ) {
return Math.floor(Math .random() * ( 1 + high - low ) +
low );
}

// fill a new array "randomNumb er" sequentially
for( ii=1; ii<=5; ii++ ) {
randomlist[ ii ] = ii;
}

// randomize the randomNumber array by record swapping
for( ii=1; ii<=5; ii++ ) {
var randomNumber = Random( 1, 5 );
var temp = randomlist[ ii ]
randomlist[ ii ] = randomlist[ randomNumber ]
randomlist[ randomNumber ] = temp
}

// indirect output the so randomized list
for( ii=1; ii<=5; ii++ ) {
document.write( unSorted[randomlist[ ii ]]+"<br>")

// or fill a new array "myNewArray ":
// myNewArray[ ii ] = unSorted[randomlist[ ii ]]
}

</script>

--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

Jul 23 '05 #9

Michael Winter

On Fri, 2 Apr 2004 14:12:22 +1200, Nik Coughin <nr***********@ woosh.co.nz>
wrote:

Nik Coughin wrote:

[snip]

To be honest, I don't know if it saves resources or even if it's
necessary. I don't know all that much about JavaScript, just the
basic syntax. I'm just lucky that it's similar enough to other
languages that I've used that pretty much everything I write works
first time (except when I type something out quickly and sloppily and
fuck up the capitalisation) . I've written in a lot of different
languages (BASIC, Pascal, COBOL [yuck], c/c++, vb, DarkBASIC, delphi,
JavaScript, *nix shell, etc. etc. etc.), and I've gotten into the
habit of declaring arrays before I use them.

That said, looking through the Wrox JavaScript Programmer's Reference, it
seems that they either need to be or should be declared.

You need to initialise the variable or property to be of an array type
using either of

a = [];
a = new Array();

but you needn't specify a size. Writing

a[ 7 ] = 'The only entry';

will resize the zero-length array to include eight elements, the last of
which contains a string. The first seven will remain undefined: a sparse
array.

There might be some speed improvements by specifying an adequate initial
size, but only if arrays in JavaScript are implemented as contiguous
memory blocks, which might not be the case (probably implementation
dependent).

The same is true for an object. You need to initialise the variable or
property to an object using either of[1]

o = {};
o = new Object();

before you assign any properties or methods.

Mike
[1] You could also use a function as a constructor.

--
Michael Winter
M.******@blueyo nder.co.invalid (replace ".invalid" with ".uk" to reply)

Jul 23 '05 #10

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