quick sort in javascript code example

Example 1: quick sort in javascript

function quicksort(array) {
  if (array.length <= 1) {
    return array;
  }

  var pivot = array[0];
  
  var left = []; 
  var right = [];

  for (var i = 1; i < array.length; i++) {
    array[i] < pivot ? left.push(array[i]) : right.push(array[i]);
  }

  return quicksort(left).concat(pivot, quicksort(right));
};

Example 2: quicksort javascript

const quickSort = array =>
  (function qsort(arr, start, end) {
    if (start >= end) return arr;
    let swapPos = start;

    for (let i = start; i <= end; i++) {
      if (arr[i] <= arr[end]) {
        [arr[swapPos], arr[i]] = [arr[i], arr[swapPos]];
        swapPos++;
      }
    }
    qsort(arr, start, --swapPos - 1);
    qsort(arr, swapPos + 1, end);

    return arr;
  })(Array.from(array), 0, array.length - 1);

Example 3: quick sort js

var items = [5, 3, 7, 6, 2, 9];

function swap(items, leftIndex, rightIndex) {
  var temp = items[leftIndex];
  items[leftIndex] = items[rightIndex];
  items[rightIndex] = temp;
}

function partition(items, left, right) {
  var pivot = items[Math.floor((right + left) / 2)], //middle element
    i = left, //left pointer
    j = right; //right pointer
  while (i <= j) {
    while (items[i] < pivot) {
      i++;
    }
    while (items[j] > pivot) {
      j--;
    }
    if (i <= j) {
      swap(items, i, j); //sawpping two elements
      i++;
      j--;
    }
  }
  return i;
}

function quickSort(items, left, right) {
  var index;
  if (items.length > 1) {
    index = partition(items, left, right); //index returned from partition
    if (left < index - 1) {
      //more elements on the left side of the pivot
      quickSort(items, left, index - 1);
    }
    if (index < right) {
      //more elements on the right side of the pivot
      quickSort(items, index, right);
    }
  }
  return items;
}

// first call to quick sort
var sortedArray = quickSort(items, 0, items.length - 1);
console.log(sortedArray); //prints [2,3,5,6,7,9]