feat(getQueryStringParam): Add getQueryStringParam function

Author: Kent C. Dodds

src/get-query-string-param.js

@@ -0,0 +1,18 @@
+export default getQueryStringParam
+
+/**
+ * Original Source: http://stackoverflow.com/a/901144/971592
+ *
+ * This method will get the value of a part of a query string in a given url
+ *
+ * @param {String} url - the url to get the value from
+ * @param {String} name - The property from the query string
+ * @return {String} - the value
+ */
+function getQueryStringParam(url, name) {
+  const regexReadyName = name.replace(/[\[]/, '\\[').replace(/[\]]/, '\\]')
+  const regex = new RegExp('[\\?&]' + regexReadyName + '=([^&#]*)')
+  const results = regex.exec(url)
+  return results === null ? '' : decodeURIComponent(results[1].replace(/\+/g, ' '))
+}
+

src/index.js

@@ -1,4 +1,9 @@
 import flatten from './flatten'
+import getQueryStringParam from './get-query-string-param'
 import snakeToCamel from './snake-to-camel'
 
-export {flatten, snakeToCamel}
+export {
+  flatten,
+  snakeToCamel,
+  getQueryStringParam,
+}

test/get-query-string-param.test.js

@@ -0,0 +1,18 @@
+import test from 'ava'
+import {getQueryStringParam} from '../src'
+
+const url = 'https://egghead.io/?utm_source=test&utm_medium=code&utm_campaign=contributing-to-open-source'
+
+test('gets the given parameter', t => {
+  const name = 'utm_campaign'
+  const expected = 'contributing-to-open-source'
+  const actual = getQueryStringParam(url, name)
+  t.same(actual, expected)
+})
+
+test('returns an empty string if param does not exist', t => {
+  const name = 'missing-thing'
+  const expected = ''
+  const actual = getQueryStringParam(url, name)
+  t.same(actual, expected)
+})