feat(subtract): Add a "subtract" function (#60)

Closes #56

Author: naumicoder

src/index.js

@@ -14,6 +14,7 @@ import isNullOrWhitespace from './is-null-or-whitespace'
 import startsWith from './startsWith'
 import removeDuplicates from './remove-duplicates'
 import add from './add'
+import subtract from './subtract'
 
 export {
   flatten,
@@ -32,4 +33,5 @@ export {
   startsWith,
   removeDuplicates,
   add,
+  subtract,
 }

src/subtract.js

@@ -0,0 +1,13 @@
+export default Subtract
+
+/**
+ * @module Subtract
+ * @Description This method will perform Subtract operation.
+ *
+ * @param {Number} num1 - first number for Subtraction
+ * @param {Number} num2 - second  number for Subtraction
+ * @return {Number} - Result of Subtraction
+ */
+function Subtract(num1, num2) {
+  return num1 - num2
+}

test/subtract-test.js

@@ -0,0 +1,10 @@
+import test from 'ava'
+import {subtract} from '../src'
+
+test('subtract two integers ', t => {
+  const number1 = 30
+  const number2 = 12
+  const expected = 30 - 12
+  const actual = subtract(number1, number2)
+  t.deepEqual(actual, expected)
+})