From e0883facdb782af176e4897efe043563cabc0eb8 Mon Sep 17 00:00:00 2001
From: Yosapol Jitrak <yosapoljittarak@hotmail.com>
Date: Fri, 16 Oct 2020 16:31:40 +0700
Subject: [PATCH 1/4] Refactor Maths/Factorial for more minimal side effects.

---
 Maths/Factorial.js           | 32 ++++++++++----------------------
 Maths/test/Factorial.test.js |  3 ---
 2 files changed, 10 insertions(+), 25 deletions(-)

diff --git a/Maths/Factorial.js b/Maths/Factorial.js
index 04d9ef08c..80daa168b 100644
--- a/Maths/Factorial.js
+++ b/Maths/Factorial.js
@@ -14,36 +14,24 @@
 'use strict'
 
 const calcRange = (num) => {
-  // Generate a range of numbers from 1 to `num`.
-  let i = 1
-  const range = []
-  while (i <= num) {
-    range.push(i)
-    i += 1
-  }
-  return range
+  return [...Array(num).keys()].map(i => i + 1);
 }
 
 const calcFactorial = (num) => {
-  let factorial
-  const range = calcRange(num)
 
-  // Check if the number is negative, positive, null, undefined, or zero
-  if (num < 0) {
-    return 'Sorry, factorial does not exist for negative numbers.'
-  }
-  if (num === null || num === undefined) {
-    return 'Sorry, factorial does not exist for null or undefined numbers.'
+  if (num > 0) {
+    const range = calcRange(num)
+    const factorial = range.reduce((a, c) => a * c, 1);
+    return `The factorial of ${num} is ${factorial}`
   }
   if (num === 0) {
     return 'The factorial of 0 is 1.'
   }
-  if (num > 0) {
-    factorial = 1
-    range.forEach(function (i) {
-      factorial = factorial * i
-    })
-    return `The factorial of ${num} is ${factorial}`
+  if (num < 0) {
+    return 'Sorry, factorial does not exist for negative numbers.'
+  }
+  if (!num) {
+    return 'Sorry, factorial does not exist for null or undefined numbers.'
   }
 }
 
diff --git a/Maths/test/Factorial.test.js b/Maths/test/Factorial.test.js
index bd22ad436..31c6cee39 100644
--- a/Maths/test/Factorial.test.js
+++ b/Maths/test/Factorial.test.js
@@ -1,9 +1,6 @@
 import { calcFactorial } from '../Factorial'
 
 describe('calcFactorial', () => {
-  it('is a function', () => {
-    expect(typeof calcFactorial).toEqual('function')
-  })
 
   it('should return a statement for value "0"', () => {
     expect(calcFactorial(0)).toBe('The factorial of 0 is 1.')

From 301a8dd19ae695e2e072c119c63b32e3c884f671 Mon Sep 17 00:00:00 2001
From: Yosapol Jitrak <yosapoljittarak@hotmail.com>
Date: Fri, 16 Oct 2020 16:35:42 +0700
Subject: [PATCH 2/4] Fix Extra semicolon and Block must not be padded by blank
 lines.

---
 Maths/Factorial.js           | 4 ++--
 Maths/test/Factorial.test.js | 1 -
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/Maths/Factorial.js b/Maths/Factorial.js
index 80daa168b..327ea316b 100644
--- a/Maths/Factorial.js
+++ b/Maths/Factorial.js
@@ -14,14 +14,14 @@
 'use strict'
 
 const calcRange = (num) => {
-  return [...Array(num).keys()].map(i => i + 1);
+  return [...Array(num).keys()].map(i => i + 1)
 }
 
 const calcFactorial = (num) => {
 
   if (num > 0) {
     const range = calcRange(num)
-    const factorial = range.reduce((a, c) => a * c, 1);
+    const factorial = range.reduce((a, c) => a * c, 1)
     return `The factorial of ${num} is ${factorial}`
   }
   if (num === 0) {
diff --git a/Maths/test/Factorial.test.js b/Maths/test/Factorial.test.js
index 31c6cee39..a06519477 100644
--- a/Maths/test/Factorial.test.js
+++ b/Maths/test/Factorial.test.js
@@ -1,7 +1,6 @@
 import { calcFactorial } from '../Factorial'
 
 describe('calcFactorial', () => {
-
   it('should return a statement for value "0"', () => {
     expect(calcFactorial(0)).toBe('The factorial of 0 is 1.')
   })

From 57e20c551c294dc3cadadd473c1b188770e566c0 Mon Sep 17 00:00:00 2001
From: Yosapol Jitrak <yosapoljittarak@hotmail.com>
Date: Fri, 16 Oct 2020 16:38:34 +0700
Subject: [PATCH 3/4] Fix Block must not be padded by blank lines.

---
 Maths/Factorial.js | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Maths/Factorial.js b/Maths/Factorial.js
index 327ea316b..c3a0162e4 100644
--- a/Maths/Factorial.js
+++ b/Maths/Factorial.js
@@ -18,7 +18,6 @@ const calcRange = (num) => {
 }
 
 const calcFactorial = (num) => {
-
   if (num > 0) {
     const range = calcRange(num)
     const factorial = range.reduce((a, c) => a * c, 1)

From 285d2b08da905496e9fe9c2f31fd3d8501d6893b Mon Sep 17 00:00:00 2001
From: Ejiah <yosapoljittarak@hotmail.com>
Date: Fri, 22 Jan 2021 12:44:52 +0700
Subject: [PATCH 4/4] Move the (num > 0) if condition to the end

---
 Maths/Factorial.js | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/Maths/Factorial.js b/Maths/Factorial.js
index c3a0162e4..29b416a67 100644
--- a/Maths/Factorial.js
+++ b/Maths/Factorial.js
@@ -18,11 +18,6 @@ const calcRange = (num) => {
 }
 
 const calcFactorial = (num) => {
-  if (num > 0) {
-    const range = calcRange(num)
-    const factorial = range.reduce((a, c) => a * c, 1)
-    return `The factorial of ${num} is ${factorial}`
-  }
   if (num === 0) {
     return 'The factorial of 0 is 1.'
   }
@@ -32,6 +27,11 @@ const calcFactorial = (num) => {
   if (!num) {
     return 'Sorry, factorial does not exist for null or undefined numbers.'
   }
+  if (num > 0) {
+    const range = calcRange(num)
+    const factorial = range.reduce((a, c) => a * c, 1)
+    return `The factorial of ${num} is ${factorial}`
+  }
 }
 
 export { calcFactorial }