feat: adds an 'isFunction' function (#102)

* feat: adds an 'isFunction' function

Closes #100

* refactor: removes package-lock.json and adds to .gitignore

removes package-lock.json and adds to .gitignore

Author: mitchellporter

.gitignore

@@ -4,3 +4,4 @@ node_modules
 .nyc_output/
 coverage/
 npm-debug.log
+package-lock.json

src/index.js

@@ -34,6 +34,7 @@ import swapCase from './swap-case'
 import endsWith from './endsWith'
 import round from './round'
 import checkPalindrome from './checkPalindrome'
+import isFunction from './is-function'
 
 export {
   isEven,
@@ -72,4 +73,5 @@ export {
   endsWith,
   round,
   checkPalindrome,
+  isFunction,
 }

src/is-function.js

@@ -0,0 +1,14 @@
+export default isFunction
+
+/**
+ * Original source: https://stackoverflow.com/a/7356528/3344977
+ *
+ * This method checks whether an object passed as an
+ * argument is a javascript Function or not
+ * @param {Object} functionToCheck - the object to check
+ * @return {Boolean} - true if functionToCheck is a function else false
+*/
+function isFunction(functionToCheck) {
+  const getType = {}
+  return functionToCheck && getType.toString.call(functionToCheck) === '[object Function]'
+}

test/is-function.test.js

@@ -0,0 +1,37 @@
+import test from 'ava'
+import {isFunction} from '../src'
+
+test('check a function', t => {
+  const func = () => {}
+  const expected = true
+  const actual  = isFunction(func)
+  t.deepEqual(actual, expected)
+})
+
+test('check an object', t => {
+  const object = {}
+  const expected = false
+  const actual = isFunction(object)
+  t.deepEqual(actual, expected)
+})
+
+test('check a string', t => {
+  const string = 'string'
+  const expected = false
+  const actual = isFunction(string)
+  t.deepEqual(actual, expected)
+})
+
+test('check a boolean', t=> {
+  const boolean = true
+  const expected = false
+  const actual = isFunction(boolean)
+  t.deepEqual(actual, expected)
+})
+
+test('check a number', t => {
+  const number = 1
+  const expected = false
+  const actual = isFunction(number)
+  t.deepEqual(actual, expected)
+})