select random value NOT in array

Question

How would I select a random value (0 to 30) that is not in this array?

var list = new Array(1,3,4,7,8,9);

Answer 1

function RandomValueNotInArray(array)
{
    var e;
    do
    {
        e = Math.random() * 31; // n + 1
    } while (array.contains(e))
    return e;
}

Answer 2

Build the complementary array and pick random values from it.

var list2 = new Array();
for(var i=0; i<30; i++)
  if(!list.contains(i))
    list2.push(i);

Then:

var rand = list2[Math.floor(Math.random() * list2.length)];

Answer 3

Assuming your list is reasonable small in size, create a list of numbers that are not in the array and then select a number from that array at random.