From 34fdbe917300bdd515cf1692877df0a0be1fbf37 Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Thu, 14 Dec 2017 10:46:46 +0200
Subject: [PATCH] Build README

---
 README.md                          | 16 ++++++++++++++++
 snippets/{group-by => group-by.md} |  2 +-
 2 files changed, 17 insertions(+), 1 deletion(-)
 rename snippets/{group-by => group-by.md} (94%)

diff --git a/README.md b/README.md
index 8b9c31e13..522f36584 100644
--- a/README.md
+++ b/README.md
@@ -38,6 +38,7 @@
 * [Get native type of value](#get-native-type-of-value)
 * [Get scroll position](#get-scroll-position)
 * [Greatest common divisor (GCD)](#greatest-common-divisor-gcd)
+* [Group by](#group-by)
 * [Hamming distance](#hamming-distance)
 * [Head of list](#head-of-list)
 * [Initial of list](#initial-of-list)
@@ -383,6 +384,21 @@ const gcd = (x, y) => !y ? x : gcd(y, x % y);
 // gcd (8, 36) -> 4
 ```
 
+### Group by
+
+Use `Array.map()` to map the values of an array to a function or property name.
+Use `Array.reduce()` to create an object, where the keys are produced from the mapped results.
+
+```js
+const groupBy = (arr, func) =>
+  (typeof func === 'function' ? arr.map(func) : arr.map(val => val[func]))
+    .reduce((acc, val, i) => {
+      acc[val] = acc[val] === undefined ? [arr[i]] : acc[val].concat(arr[i]); return acc;
+    }, {});
+// groupBy([6.1, 4.2, 6.3], Math.floor) -> {4: [4.2], 6: [6.1, 6.3]}
+// groupBy(['one', 'two', 'three'], 'length') -> {3: ['one', 'two'], 5: ['three']}
+```
+
 ### Hamming distance
 
 Use XOR operator (`^`) to find the bit difference between the two numbers, convert to binary string using `toString(2)`.
diff --git a/snippets/group-by b/snippets/group-by.md
similarity index 94%
rename from snippets/group-by
rename to snippets/group-by.md
index e6df1a2a7..ab833c9d2 100644
--- a/snippets/group-by
+++ b/snippets/group-by.md
@@ -4,7 +4,7 @@ Use `Array.map()` to map the values of an array to a function or property name.
 Use `Array.reduce()` to create an object, where the keys are produced from the mapped results.
 
 ```js
-const groupBy = (arr, func) => 
+const groupBy = (arr, func) =>
   (typeof func === 'function' ? arr.map(func) : arr.map(val => val[func]))
     .reduce((acc, val, i) => {
       acc[val] = acc[val] === undefined ? [arr[i]] : acc[val].concat(arr[i]); return acc;