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Random array in AS2 & AS3 example using sort

I suppose many of you know how to use sort to get random array…
For those who are not familiar with those nice feature of sort method I will explain the idea. Sort method can randomize array if you put function that return -1, 0 or 1 randomly, which basiclly tells sort randomly are elements less then, equal or greater then eash other.

AS2 Random Array based on Sort source:

var a:Array = new Array(“a”, “b”, “c”, “d”, “e”);
function shuffle(a,b):Number {
var num : Number = Math.round(Math.random()*2)-1;
return num;
var b:Array = a.sort(shuffle);

AS2 Random Array based on Sort source:

var a:Array = new Array(“a”, “b”, “c”, “d”, “e”);
function shuffle(a,b):int {
var num : int = Math.round(Math.random()*2)-1;
return num;
var b:Array = a.sort(shuffle);

EDIT: you can take a look at algo comparison, with source for much faster approach in new post


28 thoughts on “Random array in AS2 & AS3 example using sort

  1. rick says:

    i tried your random adn it works great but i am trying to apply this to a multidimensional array and it doesn’t work. any suggestions?

  2. how exactly you would like to sort a multidimensional array?

    give me an example and I will try to provide an example

    also I will soon post much more faster array sort method

  3. rick says:

    well i ama creating a map out of a 2D array. Rows and columns like a checker board. the catch is it is simulating a 3D griad with walls and floor tiles. I gave each a numerical value of 100= floor and 200= wall. This is for a collision detection. If 200> cant go past. I want to keep the outer walls at 200 for a borader so all of row1 and lastrow will be 200 and the begining index and last index of every array in between will = 200. All the remaining indexes i want to randomize with the value of 100 or 200. Essentially creating a random maze.

  4. well, seems like this function won’t do it for you
    this is for randomizing an array (indexes of array) so
    a,b,c,d becomes b,c,a,d or d,c,a,b

    for your idea if I understood it good following lines could help

    for (var i:Number;i

  5. rick says:

    I tried using your nested loop and tweeked it a bit. Now i can’t get the if statement to work. i keep getting a value of 200 in places i don’t want. Any ideas why?

    // 2D array
    var gridsize:Number = 10;
    // creating the map
    var map_ray:Array = new Array(gridsize);
    var i:Number;
    var j:Number;

    //incrementing the col to = gridsize
    for (i=0; i

  6. Pingback: Randomize Array - Shuffle an array in Flash « Cyberspace Nova

  7. don’t be sorry
    looking at your article and as I knowing math good I can agree it’s not ultimate array shuffle, but it’s good for beginners
    stating it won’t shuffle pack of cards good is not true
    pack of cards are shuffle good and good enough, taking it in long runs can lead to some cards show more times on one then another, that is true

    your splice algorithm lacks on speed, I made another article which I found time to do know after you made your point ;

  8. Pingback: Array Aleatorios en AS2 » unijimpe

  9. Pingback: Array Aleatorios en AS2 «

  10. Agustin says:

    wow!!! just now.
    With your code I gave a second look to the Array.sort() method, and finally I can make sense to issues I had given up on.
    One never stops learning, even about things you thought you knew well.
    It’s a very efficient way to shuffle an array.
    Thanks a lot, I was looking for a way less elegant solution, this is great.

  11. Using “while” instead of “for”, as in the following function, reduces the processing time from 4 ms to 1 ms! So the stats are (Methods 1-4 are original, Method 5 is the while loop):

    Method 1, time: 718
    Method 2, time: 1957
    Method 3, time: 3
    Method 4, time: 4
    Method 5 (while), time: 1


    function mixArray(array:Array):Array {
    var _length:Number = array.length, mixed:Array = array.slice(), rn:Number, it:Number, el:Object;
    while (it < _length) {
    el = mixed[it];
    mixed[it] = mixed[rn = it + random(_length – it)];
    mixed[rn] = el;
    return mixed;

  12. Amazing sir. This is by far one of the best solutions I’ve found yet.

    Thanks alot, really appreciate you providing this for everyone around you.

  13. Pingback: 2010 in review « Cyberspace Nova

  14. As Alec McEachran seems to explain (although his link is broken), this function is slick and fast, but it’s not good if you want an even randomization. What I call an even randomization is for each item, to have a probability of 1/N to be found at any place in the randomized array.

    So if you’re going to call this function several times and want each result as different as possible from the previous, you should consider the splice method instead.

    More explanation can be found here :

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  18. sandy says:

    Hey can you help me to create 2 elements randomize array or pick two indexed array and put it randomly
    so it should be like this

    before using random function [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]
    after using random function [ 5, 6, 1, 2, 9, 10, 3, 4, 7, 8 ] or [9,10,1,2,7,8,3,4,5,6]
    it always produce 1 before 2, 3 before 4, 5 before 6 and so on. Then put it randomly
    it will be impossible to produce 2,1 or 10,9 or 6,5 and so on,

    it will random 2 elements, not 1 by 1 but 2 by 2. Sorry for my bad English. I hope you understand what i mean.

  19. hi wonder could anyone shed some light on how to create an array with ten audio questions picked randomly (add child from library) and using the left arrow, up arrow, right arrow to pick the answer from the A B or C options given, i also want the text questions displayed on stage, so i presume the random audio question would have to be selected first and when selected a timer will kick in some three seconds later to display the identical question, so as the child could see … the answers to the text questions will also be in an array like such…

    var audioArray:Array = new Array [“quest1.wav”,”quest2.wav”,”quest3.wav”,”quest4.wav”,”quest5.wav”,”quest5.wav”,”quest7″,”quest8″,”quest9″,”quest10″];
    var voice:String = audioArray[Math.floor(Math.random() * (audioArray.length – 1))];

    var newArray:Array = new Array();
    function randomizeArray(array:Array):Array
    var newArray:Array = new Array();

    while (array.length > 0) // for ( var o:int = 0; o <20; o++)
    newArray.push(array.splice(Math.floor(Math.random()*array.length), 1));
    return newArray;

    var myQuest:Array = new quest();
    I also need addChild(); to bring the audio from the library

    var questions:Array =["Where is Dublin? ","What is gold? ","Name the Cat species? ","What is the capital of Peru?","What date does Christmas day fall on? ","State the colour Of Daffodils? ","What are the initials for America ","How many fingers has a bird","What do you boil to make tea with","Where does families usually go in Summer "];

    var answers:Array=[ ["Ireland","Wales","Scotland"], ["Fabric","Metal","Plastic"], ["Bovine","Equine","Feline"] ,[ "Lima","Arizona","Cologne"] ,["1st April","25th December","30th June"], ["Yellow","Red","Purple"], ["AMC","MER","USA"] ,[ "two","none","three"] ,
    ["Water","Milk","Olive Oil"], ["To bed","To Work","On Holiday"], ];

    I am putting the answers in such a way to be able to correspond with the question
    (So the first set of brackets will always display where the correct answer lies)

    Finally, each single question must be answered correctly before the program moves on to the next question PLUS I want only three questions to be chosen in the game each time.
    I really hope someone can give me some insight into how i proceed, i have tried several combinations, but so far to no avail

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