feat(fibonacciSum): finding the sum of fibonacci series (#184)

I've added a fibonacciSum function which return the sum of the fib series for the given number.

closes #132

.gitignore

@@ -4,4 +4,5 @@ node_modules
 .nyc_output/
 coverage/
 npm-debug.log
-package-lock.json
+package-lock.json
+.vscode

src/fibonacciSum.js

@@ -0,0 +1,28 @@
+export default fibonacciSum
+
+/**
+ * Original Source: https://stackoverflow.com/a/31388603
+ *
+ * Function that returns the sum of a fib series
+ *
+ * @param  {Number} num - A number
+ * @return {Number}     - sum of the numbers
+ */
+
+function fibonacciSum(num) {
+  if (num <= 0) {
+    return 0
+  }
+  const fib = []
+  fib[0] = 0
+  fib[1] = 1
+  let sum = fib[0] + fib[1]
+    // remaining numbers
+  for (let i = 2; i <= num; i++) {
+    fib[i] = fib[i - 1] + fib[i - 2]
+    sum += fib[i]
+  }
+  return sum
+}
+
+

src/index.js

@@ -65,6 +65,7 @@ import removeElementFromArray from './removeElementFromArray'
 import generatePassword from './generate-password'
 import tail from './tail'
 import makeObjectIterable from './makeObjectIterable'
+import fibonacciSum from './fibonacciSum'
 
 export {
   reverseArrayInPlace,
@@ -134,4 +135,5 @@ export {
   generatePassword,
   tail,
   makeObjectIterable,
+  fibonacciSum,
 }

test/fibonacciSum.test.js

@@ -0,0 +1,30 @@
+import test from 'ava'
+import {fibonacciSum} from '../src'
+
+test('valid number', t => {
+  const num = 5
+  const expected = 12
+  const result = fibonacciSum(num)
+  t.is(expected, result)
+})
+
+test('invalid number', t => {
+  const num = -5
+  const expected = 0
+  const result = fibonacciSum(num)
+  t.is(expected, result)
+})
+
+test('number in quotes', t => {
+  const num = '10'
+  const expected = 143
+  const result = fibonacciSum(num)
+  t.is(expected, result)
+})
+
+test('decimal number', t => {
+  const num = 12.1
+  const expected = 376
+  const result = fibonacciSum(num)
+  t.is(expected, result)
+})