Shuffle an array using the Pencil-and-paper method
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Fisher–Yates shuffle
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| function( | |
| a, // an array | |
| b // placeholder | |
| ){ | |
| for(b=a.length ;b ;) | |
| a.push(a.splice(Math.random()*b--,1)[0]) // randomly move an element to the end | |
| } |
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| function(a,b){for(b=a.length;b;)a.push(a.splice(Math.random()*b--,1)[0])} | |
| function(a){with(a)for(a=length;a;)push(splice(Math.random()*a--,1)[0])} // with version and save 1 byte thanks to @subzey |
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| DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE | |
| Version 2, December 2004 | |
| Copyright (C) 2011 YOUR_NAME_HERE <YOUR_URL_HERE> | |
| Everyone is permitted to copy and distribute verbatim or modified | |
| copies of this license document, and changing it is allowed as long | |
| as the name is changed. | |
| DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE | |
| TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION | |
| 0. You just DO WHAT THE FUCK YOU WANT TO. |
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| { | |
| "name": "shuffle", | |
| "description": "Shuffle an array.", | |
| "keywords": [ | |
| "Fisher–Yates", | |
| "shuffle", | |
| "array" | |
| ] | |
| } |
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| <!DOCTYPE html> | |
| <title>Foo</title> | |
| <div>Expected value: <b>Random numbers</b></div> | |
| <div>Actual value: <b id="ret"></b></div> | |
| <script> | |
| // write a small example that shows off the API for your example | |
| // and tests it in one fell swoop. | |
| var myFunction = function(a,b){for(b=a.length;b;)a.push(a.splice(Math.random()*b--,1)[0])} | |
| var a = [1,2,3,4,5,6,7,8,9]; | |
| myFunction(a); | |
| document.getElementById( "ret" ).innerHTML = a | |
| </script> |
It looks like you don't need to cast the first argument of splice into an int, the function already does it.
[1, 2, 3].splice(1, 1)
> [2]
[1, 2, 3].splice(1.2, 1)
> [2]
I tested it on ie9, chrome, firefox and opera. Not sure if it works on all versions but I suppose it would
you can make it shorter
function(a,b){for(b in a)a.push(a.splice(Math.random()*b,1))}
@williammalo: Thanks for you advice!
But I am afraid that there will be an error if you input a non-array object.
@tsaniel: "for in" loops also work with objects, for example: {foo:bar,lorem:ipsum} if thats whats bothering you.
If you don't change your own function, I'll make a fork =D
I think an object does not have methods "push" and "splice"...
Anyway, feel free to fork the code :)
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Thanks, the
withtrick is awesome!However, I think it's not worth it.
Actually,
.sort(function(){return.5-Math.random()})can be the shortest code but inefficient.