Fisher-Yates

Produced an unbiased permutation: every permutation is equally likely.

Pseudocode:

Algorithm 1 Fisher-Yates shuffle

Require: An array $A$ of length $n$

1:for $i = n-1$ to $1$ do

2:$j \gets$ random integer such that $0 \leq j \leq i$

3:swap $A[i]$ and $A[j]$

4:end for

Implementation of modern Fisher-Yates algorithm

FisherYates.js

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);
}