Added InsertionSort algorithm implementation and test

Author: ialixandroae

sorting/insertion-sort.js

@@ -0,0 +1,35 @@
+/**
+ * Implement [Insertion sort]
+ *
+ * Copyright (c) 2018, Ionut Alixandroae.
+ * Licensed under the MIT License.
+ */
+
+'use strict';
+
+/**
+ * Bubble sort algorithm.
+ * Complexity: O(N^2).
+ *
+ * @example
+ * console.log(insertionSort([54, 26, 93, 17, 77, 31, 44, 55, 20])); // [ 17, 20, 26, 31, 44, 54, 55, 77, 93 ]
+ *
+ * @public
+ * @module sorting/insertionsort
+ * @param {Array} array Input array.
+ * @return {Array} Sorted array.
+ */
+function insertionSort(array) {
+  for (var i = 0; i < array.length; i++) {
+    var temp = array[i];
+    var j = i - 1;
+    while (j >= 0 && array[j] > temp) {
+      array[j + 1] = array[j];
+      j--;
+    }
+    array[j + 1] = temp;
+  }
+  return array;
+}
+
+module.exports = insertionSort;

tests/sorting/insertion-sort.spec.js

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+const chai = require('chai');
+const expect = chai.expect;
+const sort = require('../../sorting/insertion-sort.js');
+
+describe('Insertion sort', function() {
+  it('should work with empty arrays', function() {
+    expect(sort([])).deep.equal([]);
+  });
+
+  it('should work with sorted arrays', function() {
+    expect(sort([1, 2, 3, 4])).to.have.ordered.members([1, 2, 3, 4]);
+  });
+
+  it('should work with non-sorted arrays', function() {
+    let array = [2, 5, 1, 0, 4, 3];
+    array = sort(array);
+    for (let i = 0; i < array.length - 1; i += 1) {
+      expect(array[i] <= array[i + 1]).to.be.true;
+    }
+  });
+});