How to randomize subset of array in Javascript?

Question

What is the best way to randomize part of the array in Javascript

For example, if I have 100 items in the array, what is the fast and efficient way of randomizing set of

Answer 1

The following shuffles the specified chunk of an array in place, as randomly as the environment's random number generator will allow:

function shuffleSubarray(arr, start, length) {
    var i = length, temp, index;
    while (i--) {
        index = start + Math.floor(i * Math.random());
        temp = arr[index];
        arr[index] = arr[start + i];
        arr[start + i] = temp;
    }
    return arr;
}

var a = [1, 2, 3, 4, 5, 6, 7, 8, 9];
alert( shuffleSubarray(a, 2, 5) );