feat(isNullOrWhitespace): Add isNullOrWhitespace function

Closes #45

Author: Adam Eury

src/index.js

@@ -10,6 +10,7 @@ import getObjectSize from './get-object-size'
 import isArray from './is-array'
 import validateEmail from './validateEmail'
 import hex2rgb from './hex2rgb'
+import isNullOrWhitespace from './is-null-or-whitespace'
 
 export {
   flatten,
@@ -24,4 +25,5 @@ export {
   isArray,
   validateEmail,
   hex2rgb,
+  isNullOrWhitespace,
 }

src/is-null-or-whitespace.js

@@ -0,0 +1,14 @@
+export default isNullOrWhitespace
+
+/**
+ * Original Source: http://stackoverflow.com/a/32800728
+ *
+ * This method checks whether a string passed as an
+ * argument is undefined, null, empty, or whitespace.
+ *
+ * @param {String} str - The string to check
+ * @return {Boolean} - True if str is undefined, null, empty, or whitespace else false
+ */
+function isNullOrWhitespace(str) {
+  return !str || !str.trim()
+}

test/is-null-or-whitespace.test.js

@@ -0,0 +1,33 @@
+import test from 'ava'
+import {isNullOrWhitespace} from '../src'
+
+test('check undefined', t => {
+  const expected = true
+  const actual = isNullOrWhitespace(undefined)
+  t.deepEqual(actual, expected)
+})
+
+test('check null', t => {
+  const expected = true
+  const actual = isNullOrWhitespace(null)
+  t.deepEqual(actual, expected)
+})
+
+test('check an empty string', t => {
+  const expected = true
+  const actual = isNullOrWhitespace('')
+  t.deepEqual(actual, expected)
+})
+
+test('check a string of whitespace', t => {
+  const expected = true
+  const actual = isNullOrWhitespace('  ')
+  t.deepEqual(actual, expected)
+})
+
+test('check a string with characters', t => {
+  const expected = false
+  const actual = isNullOrWhitespace('hello world')
+  t.deepEqual(actual, expected)
+})
+