Generating random numbers in an array without any duplicate numbers

Question

I'm trying to create an array with random number with length of 78. I don't know how to search the entire array and check if last entry was duplicate and remove it. Someone please help.

function initAll() {
var balls = LoadInBingoBalls();
for(i=0; i < balls.length;i++)
        {
            (balls[i]);
        }
    }

function setSquare (numSquare) {
    var BingoSquare = "square" + numSquare.toString();

    document.getElementById(BingoSquare).innerHTML  = RandomNumber(MaxNo);
}

var RandomNumber = function (max) {
return Math.floor(Math.random() * max) + 1;
}

function LoadInBingoBalls(){

var first = 0;
var last = 78;
var random;

 var bag = [];

//Heres the part i get confused!
for (var i = first; i <= last; i++) {

do
         bag.push(i) = setSquare(i);

    while(bag.indexOf(i) !== -1)             
  }

 return bag;
 }
 }

You have to create an array with all numbers from 1 to 78, then pop one by one randomly until you qet all balls. — Adam Calvet Bohl, Apr 27 '16 at 19:03
"Someone please help." isn't a question. Please review [ask]. — zzzzBov, Apr 27 '16 at 19:05
Does OP want numbers from 1 to 78 randomized, or 78 random numbers? — Chara, Apr 27 '16 at 19:06
Possible duplicate of [Creating random numbers with no duplicates](http://stackoverflow.com/questions/4040001/creating-random-numbers-with-no-duplicates) — Chara, Apr 27 '16 at 19:08

score 2 · Answer 1 · answered Apr 27 '16 at 19:11

2

This function will create the array and check to see if it contains the number before pushing:

working example: https://jsbin.com/cabofa/1/edit?js,console

function randNum (max) {
return Math.floor(Math.random() * max) + 1;
}

function makeArray(n) {
  var arr = [];
  while (arr.length < n) {
    var random = randNum(n);
    if (arr.indexOf(random) === -1) {
      arr.push(random);
    }
  }
  return arr;
}

answered Apr 27 '16 at 19:11

omarjmh

13,632
6
34
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if (arr.indexOf(random) === -1) { what does the -1 mean here... – Haroon Mehdi Apr 27 '16 at 19:26
indexOf returns the index of the number or -1: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf – omarjmh Apr 27 '16 at 19:30
is there any way to do this with a for loop instead of while loop? – Haroon Mehdi Apr 27 '16 at 20:38
No... You don't know how many times to loop – omarjmh Apr 27 '16 at 20:39

Dan H · Answer 2 · 2016-04-27T20:08:05.007

0

Create an array with all the possible values:

var possibles = [];

for(i=1; i<=78; i++) {
    possibles.push(i);
}

Shuffle that array of values to be random:

function shuffle(a) {
    var j, x, i;
    for (i = a.length; i; i -= 1) {
        j = Math.floor(Math.random() * i);
        x = a[i - 1];
        a[i - 1] = a[j];
        a[j] = x;
    }

    return a;
}

var shuffled = shuffle(possibles);

Now pop a value from your new array to get a random element from it:

var popped = shuffled.pop();
console.log(popped);

You can call pop() as many times as you want until the array is empty, which will return undefined. For example:

for(i=0; i<shuffled.length; i++) {
    console.log(shuffled.pop());
}

edited Apr 27 '16 at 20:08

answered Apr 27 '16 at 19:16

Dan H

3,524
3
35
46

I can't see here where you have checked for duplicates... – Haroon Mehdi Apr 27 '16 at 19:30
No need to check for duplicates. pop() will remove the last element from the array which has already been shuffled. I have edited my answer and added a final example. Run that in a console and you will get random elements from 1 to 78 without duplicates. – Dan H Apr 27 '16 at 20:09

Generating random numbers in an array without any duplicate numbers

2 Answers2