quick sort

quick-sort.js

var array = [1, 7, 5, 9, 0, 4, 12, -56, 7, 0, -45, 8, 2, 3, 6, 7, 8, 1, 5, 0, 1, 7, 5, 9, 0, 4, 12, -56, 7, 0, -45, 8, 2, 3, 6, 7, 8, 1, 5, 0, 1, 7, 5, 9, 0, 4, 12, -56, 7, 0, -45, 8, 2, 3, 6, 7, 8, 1, 5, 0, 1, 7, 5, 9, 0, 4, 12, -56, 7, 0, -45, 8, 2, 3, 6, 7, 8, 1, 5, 0, 1, 7, 5, 9, 0, 4, 12, -56, 7, 0, -45, 8, 2, 3, 6, 7, 8, 1, 5, 0, 1, 7, 5, 9, 0, 4, 12, -56, 7, 0, -45, 8, 2, 3, 6, 7, 8, 1, 5, 0, 1, 7, 5, 9, 0, 4, 12, -56, 7, 0, -45, 8, 2, 3, 6, 7, 8, 1, 5, 0];

var getRandomInt = function (min, max) {
  return Math.floor(Math.random() * (max - min)) + min;
};

var quick_sort = function (unsorted) {
  if (unsorted.length === 0 || unsorted.length === 1) {
    return unsorted;
  }

  if (unsorted.length === 2) {
    return (unsorted[0] <= unsorted[1]) ? unsorted
      : unsorted.reverse();
  }


  var pivot_index = getRandomInt(0, unsorted.length);
  var pivot = unsorted[pivot_index];
  var left = [], mid = [], right = [];

  for(var i=0;i<unsorted.length;i++) {
    if (unsorted[i] < pivot) {
      left.push(unsorted[i]);
    } else if (unsorted[i] == pivot) {
      mid.push(unsorted[i]);
    } else {
      right.push(unsorted[i]);
    }
  }

  return quick_sort(left)
    .concat(mid)
    .concat(quick_sort(right));

};

var sorted = quick_sort(array);
console.log(sorted);