add quickSort.js

Author: jiangweixu

quickSort.js

@@ -0,0 +1,30 @@
+var quickSort = function (arr, left, right) {
+  var len = arr.length, pivot, partitionIndex, left = left || 0, right = right || arr.length - 1;
+  if (left < right) {
+      pivot = right;
+      partitionIndex = partition(arr, pivot, left, right);
+      quickSort(arr, left, partitionIndex - 1);
+      quickSort(arr, partitionIndex+1, right)
+  }
+  return arr;
+};
+
+function partition(arr, pivot, left, right){
+    var pivotValue = arr[pivot],
+        partitionIndex = left;
+
+    for(var i = left; i < right; i++){
+        if(arr[i] < pivotValue){
+            swap(arr, i, partitionIndex);
+            partitionIndex++;
+        }
+    }
+    swap(arr, right, partitionIndex);
+    return partitionIndex;
+}
+
+var swap = function (arr, i, j) {
+  var temp = arr[i];
+  arr[i] = arr[j];
+  arr[j] = temp;
+};