feat(reduce): reduce functionality (#78)

* feat(reduce): reduce functionality

Using Reduce to tally votes

* fix(review): addressed review comments

replaced double quotes with single

Author: yanks1987

src/index.js

@@ -1,3 +1,5 @@
+
+import reduce from './reduce-to-tally'
 import flatten from './flatten'
 import getQueryStringParam from './get-query-string-param'
 import snakeToCamel from './snake-to-camel'
@@ -24,6 +26,7 @@ import dec2bin from './dec2bin'
 import searchAndReplace from './search-and-replace'
 
 export {
+  reduce,
   flatten,
   snakeToCamel,
   getQueryStringParam,

src/reduce-to-tally.js

@@ -0,0 +1,19 @@
+export default reducer
+
+/**
+ * Original Source: https://egghead.io/courses/reduce-data-with-javascript
+ *
+ * This method will reduce duplicate values in an array,
+ * into an object with count for each individual value.
+ * @param  {Object} tallyMap - The object from which the values are taken
+ * @param  {number} vote - The vote defines a item in array
+ * @return {object} - A comma-separated Object for each individual array values with count
+ */
+function reducer(tallyMap, vote) {
+  if (tallyMap.hasOwnProperty(vote)) {
+    tallyMap[vote] = tallyMap[vote] + 1
+  } else {
+    tallyMap[vote] = 1
+  }
+  return tallyMap
+}

test/reduce-to-tally.test.js

@@ -0,0 +1,10 @@
+import test from 'ava'
+import reducer from '../src/reduce-to-tally'
+
+test('tallies an array into object with count on each', t => {
+  const initialvalue = {}
+  const original = ['angular', 'angular', 'rails', 'angular', 'Python', 'angular', 'Python', 'angular', 'Vanilla']
+  const expected = {Python: 2, Vanilla: 1, angular: 5, rails: 1}
+  const actual = original.reduce(reducer, initialvalue)
+  t.deepEqual(actual, expected)
+})