generating unique random number javascript

Question

I am trying to get random unique number and assign it to variable .for example :

var nums=[0,1,2,3,4,5,6,7];

then i have 8 variables and i want to take one of these numbers, also to be unique, every time i refresh the page. I'm not very good at Javascript, so please help.

JavaScript can't help here. Only server-side can do what you want. — VisioN
– VisioN, Commented Jan 30, 2013 at 14:00
@VisioN There could be a new JavaScript API that enables this. I'm not sure, but I think I've come across something like that a while ago. — Šime Vidas
– Šime Vidas, Commented Jan 30, 2013 at 14:05
@ŠimeVidas Well, TBH we can use localStorage and even cookies for that. But I'd go for server-side solution anyway. — VisioN
– VisioN, Commented Jan 30, 2013 at 14:10
You can do it from JS. Generate the random number r = nums[Math.floor(Math.random() * 7)] and append it to a cookie each time. — techfoobar
– techfoobar, Commented Jan 30, 2013 at 14:10
@techfoobar I don't think that Math.random() qualifies as truly random. — Šime Vidas
– Šime Vidas, Commented Jan 30, 2013 at 14:12

Jeffrey Sweeney · Accepted Answer · 2013-01-30 14:06:58Z

2

If the number only needs to be unique on the client side, it's possible. You could create a number based off the current time for example:

var id = new Date().getTime();

However, if this unique ID needs to be unique for every client, as the comments in your OP state, you'll need a server-sided solution:

var id = "<?php echo uniqid() ?>";

answered Jan 30, 2013 at 14:06

Jeffrey Sweeney

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2 Comments

dganchev Over a year ago

thank you for answering,actually i expirimented and created this code var a = Math.floor(Math.random()*6); var b =Math.floor(Math.random()*6); var c=Math.floor(Math.random()*6); var d=Math.floor(Math.random()*6); var e=Math.floor(Math.random()*6); var f=Math.floor(Math.random()*6); and then i make a while and make comparision if some of the variable mathes to loop until it`s not matching and assign it to the variables again,but this is quite long and wrong code

xr280xr Over a year ago

If you execute this pro grammatically more than once in a row, you could get a collision .

bendytree · Accepted Answer · 2013-01-30 14:34:12Z

1

First off, to get a random value from the array, you could do this:

var nums = [0,1,2,3,4,5,6,7];
var num = Math.floor(Math.random() * nums.length);

alert(num);

If you needed it to be unique, then it depends on what unique should mean. If you mean that for one user it should never repeat a number until they'd all been exhausted, then you could use a cookie to keep track of which had been shown.

answered Jan 30, 2013 at 14:34

bendytree

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Comments

RAj · Accepted Answer · 2013-01-30 14:44:10Z

0

 function randomVarGenerator()
    {
    var s4=function()
    {
       return Math.floor(Math.random(0,9)*10).toString();

    };
    return (S4() + S4() + S4() + S4()  + S4() + S4()+ S4() + S4());
    }
randomVarGenerator();

if its generating uniqueString

 function randomVarGenerator()
    {
    var s4=function()
    {
       return Math.floor(Math.random() * 0x10000 /* 65536 */).toString(16);

    };
    return (S4() + S4() + S4() + S4()  + S4() + S4()+ S4() + S4());
    }

randomVarGenerator();

edited Jan 30, 2013 at 14:44

answered Jan 30, 2013 at 14:37

RAj

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1 Comment

Chad Over a year ago

This does not guarantee uniqueness, and I don't think it is RFC compliant either. Just a simple way to get a guid-like number.

user2337191 · Accepted Answer · 2013-07-20 11:33:06Z

I guess this will be help to you. * First you should create an array that includes number. * Then you should create another array * Then randomly pick a number from this array and place it to another * After that remove the picked element from the number array.

function rand(n){

var numArr = new Array("0","1","2","3","4","5","6","7","8","9","10");


var pickArr = new Array(); 

var length=16;

for(var i=0;i<n;i++){
        var num=numArr[Math.floor((Math.random()*length))];
        pickArr[pickArr.length]=num
        length--;
        numArr.splice(findRank(numArr,num), 1);

    }


    return pickArr;
}

function findRank(seq,n){
    var cnt=0;
    var flag=true;
    for(var i=0;i<seq.length&&flag;i++){
        if(seq[i]==n)flag=false;
        else cnt++;
    }

    return cnt;
}

davidcondrey · Accepted Answer · 2015-01-08 04:05:38Z

0

var n = 4, uniqueRandoms = [];
function makeUniqueRandom() {
    if (!uniqueRandoms.length) {
        for (var i = 1; i < n; i++) {
            uniqueRandoms.push(i); // generates [1,2,3,4]
        }
    }
    var index = Math.floor(Math.random() * uniqueRandoms.length),
        val = uniqueRandoms[index];
    uniqueRandoms.splice(index, 1);
    return val;
}

makeUniqueRandom(4); // use

answered Jan 8, 2015 at 4:05

davidcondrey

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