Add quick sort (functional variant)

Author: mik-laj

src/sorting/quicksort-functional.js

@@ -0,0 +1,38 @@
+(function (exports) {
+
+  'use strict';
+
+  /**
+   * The quicksort algorithm (functional variant). It's complexity is O(nlog n).
+   *
+   * @public
+   */
+  var quickSort = (function () {
+
+    /**
+     * Sorts given array.
+     *
+     * @private
+     * @param {array} array Array which should be sorted
+     * @returns {array} array Sorted array
+     */
+    return function quickSort(array, left, right, cmp) {
+      if ( arr.length < 1) {
+        return arr;
+      }
+
+      var [x, ...rest] = arr;
+
+      return [
+          ...quickSort(rest.filter(v => v <= x)),
+          x,
+          ...quickSort(rest.filter(v => v  > x))
+      ]
+      return array;
+    }
+
+  }());
+
+  exports.quickSort = quickSort;
+
+}(typeof exports === 'undefined' ? window : exports));

test/sorting/quicksort-functional.spec.js

@@ -0,0 +1,5 @@
+var sortTestCase = require('./sort.testcase.js');
+var quickSort =
+      require('../../src/sorting/quicksort-functional.js').quickSort;
+
+sortTestCase(quickSort, 'Quick sort', { reverse: false });