This is a Javascript function that takes an array, and returns all possible permutations of the same array.

permutation.js

function permute(arr){
  return permutation(arr.sort());
}

function permutation(arr, result){
  result = typeof result !== 'undefined' ? result : [];
  result = result.concat([arr]);

  //find index k
  var k = null;
  for( var i = 0; i < (arr.length-1); i++ ){
    if (arr[i] < arr[i+1]){
      var k = i;
    }
  }
  //if k doesn't exist, we've reached the last permutation
  if (k === null){
    return result
  } 

  //otherwise proceed with finding l, and call the function again
  else {

    //find index l
    for ( var i = 0; i < arr.length; i++){
      if (arr[i] > arr[k]){
        var l = i;
      }
    }
    //swap arr[k] and arr[l] and assign it to a new variable
    var pArr = swap(arr, k, l);

    //reverse the array after arr[k]
    pArr = reverseafterk(pArr, k);

    //call permutation on the new permutated arr
    return permutation(pArr, result)

  }
}


function swap(arr, a, b){
  var i = arr[a];
  arr[a] = arr[b];
  arr[b] = i;
  return arr;
}

function reverseafterk(arr, k){
  var i = arr.splice(k+1);
  return arr.concat(i.reverse());
}