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

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)];