Produced an unbiased permutation: every permutation is equally likely.
Pseudocode:
Algorithm 2 Fisher-Yates shuffle
Require: An array of length
1:for to do
2: random integer such that
3:swap and
4:end for
Implementation of modern Fisher-Yates algorithm
function sample(obj, n, guard) {
if (n == null || guard) {
if (!isArrayLike(obj)) obj = values(obj)
return obj[random(obj.length - 1)]
}
var sample = toArray(obj)
var length = getLength(sample)
n = Math.max(Math.min(n, length), 0)
var last = length - 1
for (var index = 0; index < n; index++) {
var rand = random(index, last)
var temp = sample[index]
sample[index] = sample[rand]
sample[rand] = temp
}
return sample.slice(0, n)
}