copy the input in the length < 2 case also

and throw an Error if input is not an array.

Author: adamloving

solutions/javascript/quick-sort.js

@@ -5,9 +5,14 @@ module.exports = function quickSort(input, compare) {
       greater = [],
       pivot;
 
-  // Not an array, empty or array of 1 is already sorted
-  if (!Array.isArray(input) || input.length < 2) {
-    return input;
+  if (!Array.isArray(input)) {
+    throw new Error('Can only sort arrays.');
+  }
+
+  var array = input.slice(0); // make a copy of the array
+
+  if (array.length < 2) {
+    return array;
   }
 
   // Create a compare func if not passed in
@@ -17,8 +22,6 @@ module.exports = function quickSort(input, compare) {
     };
   }
 
-  var array = input.slice(0); // make a copy of the array
-
   // Get our pivot, this can be random
   pivot = array.splice(~~(Math.random() * array.length), 1);
 

tests/javascript/quick-sort.js

@@ -5,6 +5,17 @@ var quickSort = require('../../solutions/javascript/quick-sort');
 
 describe('Quick Sort', function(){
 
+  it('throws error if input not an array', function() {
+
+    try {
+      quickSort(null);
+    } catch (err) {
+      return;
+    }
+
+    assert(false, 'Expected exception to be thrown.');
+  });
+
   it('handles empty list', function() {
     var results = quickSort([]);
     assert(Array.isArray(results), 'Expected result to be array');