feat(reverseArrayInPlace): add reverseArrayInPlace function with tests (#169)

Author: jlkiri

src/index.js

@@ -1,3 +1,4 @@
+import reverseArrayInPlace from './reverseArrayInPlace'
 import isEven from './is-even'
 import capitalizeFirstLetter from './convert-first-letter-to-capital'
 import revstring from './revstring'
@@ -61,6 +62,7 @@ import removeAccents from './remove-accents'
 import getQueryStringValue from './get-query-string-value'
 
 export {
+  reverseArrayInPlace,
   isOdd,
   capitalizeFirstLetter,
   isEven,

src/reverseArrayInPlace.js

@@ -0,0 +1,19 @@
+export default reverseArrayInPlace
+
+/**
+ * Original Source: https://stackoverflow.com/a/41387918
+ *
+ * Function that reverses an array without creating a placeholder array.
+ *
+ * @param  {Array} array - An array
+ * @return {Array}       - A reversed array
+ */
+
+function reverseArrayInPlace(array) {
+  for (let i = 0; i < Math.floor(array.length / 2); i++) {
+    const old = array[i]
+    array[i] = array[array.length - 1 - i]
+    array[array.length - 1 - i] = old
+  }
+  return array
+}

test/reverseArrayInPlace.test.js

@@ -0,0 +1,23 @@
+import test from 'ava'
+import {reverseArrayInPlace} from '../src'
+
+test('Reverses an array in place', t => {
+  const array = [1, 2, 3, 4, 5]
+  const expected = [5, 4, 3, 2, 1]
+  const actual = reverseArrayInPlace(array)
+  t.deepEqual(actual, expected)
+})
+
+test('Reverses an empty array', t => {
+  const array = []
+  const expected = []
+  const actual = reverseArrayInPlace(array)
+  t.deepEqual(actual, expected)
+})
+
+test('Reverses an with one item', t => {
+  const array = [1]
+  const expected = [1]
+  const actual = reverseArrayInPlace(array)
+  t.deepEqual(actual, expected)
+})