Add tests for array pair sum and a working solution.

solutions/javascript/array-pair-sum.js

@@ -1,20 +1,13 @@
-module.exports = function (k, array) {
-  var hash  = {},
-      pairs = [];
+module.exports = function (sum, array) {
+  var results = [];
 
-  // Loop through the array once, storing the results in an object for a
-  // time complexity of O(n) - the naive solution consists of two for loops
-  // which results in a complexity of O(n^2)
-  array.forEach(function (number) {
-    // Make sure the value in unused and it's a unique pair
-    if (hash[k - number] === false && k - number !== number) {
-      pairs.push([number, k - number]);
-      hash[k - number] = true; // Set it to "used"
+  for (var i = 0, len = array.length; i < len; i++) {
+    for (var j = i + 1; j < len; j++) {
+      if (array[i] + array[j] === sum) {
+        results.push([array[i], array[j]]);
+      }
     }
+  }
 
-    // If the hash value is not true, set the hash to "unused"
-    !hash[k - number] && (hash[number] = false);
-  });
-
-  return pairs;
+  return results;
 };

tests/javascript/array-pair-sum.js

@@ -0,0 +1,12 @@
+var expect       = require('chai').expect;
+var arrayPairSum = require('../../solutions/javascript/array-pair-sum');
+
+describe('Array Pair Sum', function () {
+  it('should find pairs that equal the expected sum', function () {
+    expect(arrayPairSum(10, [3, 4, 5, 6, 7])).to.eql([[3, 7], [4, 6]]);
+  });
+
+  it('should allow for duplicate results', function () {
+    expect(arrayPairSum(8, [3, 4, 5, 4, 4])).to.eql([[3, 5], [4, 4], [4, 4], [4, 4]]);
+  });
+});