Solution for challenge simple encryption.

Author: levino

package-lock.json

@@ -34,5 +34,8 @@
     "prettier": "^1.14.3",
     "tap-spec": "^5.0.0",
     "tape": "^4.9.1"
+  },
+  "dependencies": {
+    "ramda": "^0.26.0"
   }
 }

package.json

@@ -1,12 +1,51 @@
-//Taken from https://www.codewars.com/kata/simple-encryption-number-1-alternating-split/javascript
+//Taken from https://www.codewars.com/kata/simple-encryption-number-1-alternating-split/javascript	
+const R = require('ramda')
+
+const even = (_, index) => (Number(index) + 1) % 2
+const odd = (_, index) => Number(index) % 2
+
 function encrypt(text, n) {
-  
+  if (n < 1 || !text) {
+    return text
+  }
+  return new Array(n)
+    .fill(0)
+    .reduce((acc) => acc.filter(odd).concat(acc.filter(even)), text.split(''))
+    .join('')
+}
+
+const splitInHalf = (inputArray) => {
+  const firstHalf = inputArray.slice(0, Math.floor(inputArray.length / 2))
+  const secondHalf = inputArray.slice(Math.floor(inputArray.length / 2))
+  if (firstHalf.length < secondHalf.length) {
+    firstHalf.push('')
+  }
+  return [firstHalf, secondHalf]
+}
+
+const reducer = (acc) => {
+  const [firstHalf, secondHalf] = splitInHalf(acc)
+  return R.pipe(
+    R.flip(R.zip)(firstHalf),
+    R.flatten,
+    R.join(''),
+    R.split('')
+  )(secondHalf)
 }
 
 function decrypt(encryptedText, n) {
+  if (n < 1 || !encryptedText) {
+    return encryptedText
+  }
+
+  return R.pipe(
+    R.reduce(reducer, encryptedText.split('')),
+    R.join('')
+  )(new Array(n).fill(0))
 }
 
 module.exports = {
   decrypt,
   encrypt,
+  splitInHalf,
 }

src/simpleEncryption.js

@@ -1,6 +1,25 @@
 const test = require('tape')
-const { decrypt, encrypt } = require('./simpleEncryption')
+const { decrypt, encrypt, splitInHalf } = require('./simpleEncryption')
 
+test('split in half', (t) => {
+  t.test('Simple', (assert) => {
+    assert.plan(1)
+    const [_, secondHalf] = splitInHalf([1])
+    assert.deepEquals(secondHalf, [1])
+  })
+  t.test('Still simple', (assert) => {
+    assert.plan(2)
+    const [firstHalf, secondHalf] = splitInHalf([1, 2])
+    assert.deepEquals(secondHalf, [2])
+    assert.deepEquals(firstHalf, [1])
+  })
+  t.test('Still simple', (assert) => {
+    assert.plan(2)
+    const [firstHalf, secondHalf] = splitInHalf([1, 2, 3])
+    assert.deepEquals(secondHalf, [2, 3])
+    assert.deepEquals(firstHalf, [1, ''])
+  })
+})
 test('Solution', function(t) {
   t.test('EncryptExampleTests', function(assert) {
     assert.equals(encrypt('This is a test!', 0), 'This is a test!')