From 675d28142251a7a317ab5928bf175e8a0eff61fd Mon Sep 17 00:00:00 2001
From: Bejamin Schachter <benschac@gmail.com>
Date: Tue, 5 Mar 2019 12:26:06 -0500
Subject: [PATCH] fix: differenceBy.md --> update differenceBy.test.js

---
 snippets/differenceBy.md  | 8 ++++----
 test/differenceBy.test.js | 4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/snippets/differenceBy.md b/snippets/differenceBy.md
index 83b3b869c..b304aab38 100644
--- a/snippets/differenceBy.md
+++ b/snippets/differenceBy.md
@@ -2,16 +2,16 @@
 
 Returns the difference between two arrays, after applying the provided function to each array element of both.
 
-Create a `Set` by applying `fn` to each element in `b`, then use `Array.prototype.filter()` in combination with `fn` on `a` to only keep values not contained in the previously created set.
+Create a `Set` by applying `fn` to each element in `b`, then use `Array.prototype.map()` to apply `fn` to each element in `a`, then `Array.prototype.filter()`
 
 ```js
 const differenceBy = (a, b, fn) => {
   const s = new Set(b.map(fn));
-  return a.filter(x => !s.has(fn(x)));
+  return a.map(fn).filter(el => !s.has(el));
 };
 ```
 
 ```js
-differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [1.2]
-differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x); // [ { x: 2 } ]
+differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [1]
+differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x); // [2]
 ```
diff --git a/test/differenceBy.test.js b/test/differenceBy.test.js
index 719f0df6b..1743f1805 100644
--- a/test/differenceBy.test.js
+++ b/test/differenceBy.test.js
@@ -5,8 +5,8 @@ test('differenceBy is a Function', () => {
   expect(differenceBy).toBeInstanceOf(Function);
 });
 test('Works using a native function and numbers', () => {
-  expect(differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor)).toEqual([1.2]);
+  expect(differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor)).toEqual([1]);
 });
 test('Works with arrow function and objects', () => {
-  expect(differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x)).toEqual([{ x: 2 }]);
+  expect(differenceBy([{ x: 2 }, { x: 1 }], [{ x: 1 }], v => v.x)).toEqual([2]);
 });