Unique random values from array of unique values javascript

Question

I have twelve squares and six of those are selected randomly and a style then applied. This is achieved by generating random values from an array of unique values. The problem

Answer 1

Just for the sake of simplicity I will assume your elements have a class.

Example on jsFiddle

So, I would grab all elements:

var elements = document.getElementsByClassName("square");

Then I would create an array with the IDs

var ids = [];

for (var i = 0; i < elements.length; ++i)
{
    ids.push(elements[i].getAttribute("id"));
}

And then generate random numbers on the length of the array

var random = roundingFunction(Math.random() * ids.length);

Then retrieve the element at the index and remove from the array

var elementID = ids.splice(random, 1);

And repeat.