From 8b58e893389dc8341965faa172d094533e702fef Mon Sep 17 00:00:00 2001
From: segayuu <segayuu@gmail.com>
Date: Thu, 15 Nov 2018 11:25:58 +0900
Subject: [PATCH 1/4] Create function: toCamelCase()

---
 lib/camel_case_keys.js | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/lib/camel_case_keys.js b/lib/camel_case_keys.js
index 6008b910..daca0ac1 100644
--- a/lib/camel_case_keys.js
+++ b/lib/camel_case_keys.js
@@ -16,6 +16,20 @@ function setter(key) {
   };
 }
 
+function toCamelCase(key) {
+  const match = key.match(rPrefixUnderscore);
+  let newKey;
+
+  if (match) {
+    const underscore = match[1];
+    newKey = underscore + camelCase(key.substring(underscore.length));
+  } else {
+    newKey = camelCase(key);
+  }
+
+  return newKey;
+}
+
 function camelCaseKeys(obj) {
   if (typeof obj !== 'object') throw new TypeError('obj must be an object!');
 
@@ -25,15 +39,7 @@ function camelCaseKeys(obj) {
   for (let i = 0, len = keys.length; i < len; i++) {
     const key = keys[i];
     const value = obj[key];
-    const match = key.match(rPrefixUnderscore);
-    let newKey;
-
-    if (match) {
-      const underscore = match[1];
-      newKey = underscore + camelCase(key.substring(underscore.length));
-    } else {
-      newKey = camelCase(key);
-    }
+    const newKey = toCamelCase(key);
 
     if (newKey === key) {
       result[key] = value;

From e9b14231dc648bd6c138ecc52987578f6d5043e7 Mon Sep 17 00:00:00 2001
From: segayuu <segayuu@gmail.com>
Date: Thu, 15 Nov 2018 11:28:08 +0900
Subject: [PATCH 2/4] Refactoring toCamelCase()

---
 lib/camel_case_keys.js | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/lib/camel_case_keys.js b/lib/camel_case_keys.js
index daca0ac1..8b2b6f14 100644
--- a/lib/camel_case_keys.js
+++ b/lib/camel_case_keys.js
@@ -16,18 +16,14 @@ function setter(key) {
   };
 }
 
-function toCamelCase(key) {
-  const match = key.match(rPrefixUnderscore);
-  let newKey;
-
-  if (match) {
-    const underscore = match[1];
-    newKey = underscore + camelCase(key.substring(underscore.length));
-  } else {
-    newKey = camelCase(key);
-  }
+function toCamelCase(str) {
+  const match = str.match(rPrefixUnderscore);
 
-  return newKey;
+  if (!match) {
+    return camelCase(str);
+  }
+  const underscore = match[1];
+  return underscore + camelCase(str.substring(underscore.length));
 }
 
 function camelCaseKeys(obj) {

From 40270ac979e53e51bdd9dde3ad07b9666aa095c2 Mon Sep 17 00:00:00 2001
From: segayuu <segayuu@gmail.com>
Date: Thu, 15 Nov 2018 11:29:14 +0900
Subject: [PATCH 3/4] Remove rPrefixUnderscore

---
 lib/camel_case_keys.js | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/lib/camel_case_keys.js b/lib/camel_case_keys.js
index 8b2b6f14..557e4fe4 100644
--- a/lib/camel_case_keys.js
+++ b/lib/camel_case_keys.js
@@ -2,8 +2,6 @@
 
 const camelCase = require('camel-case');
 
-const rPrefixUnderscore = /^(_+)/;
-
 function getter(key) {
   return function() {
     return this[key];
@@ -17,13 +15,14 @@ function setter(key) {
 }
 
 function toCamelCase(str) {
-  const match = str.match(rPrefixUnderscore);
+  let prefixLength = -1;
+
+  while (str[++prefixLength] === '_');
 
-  if (!match) {
+  if (!prefixLength) {
     return camelCase(str);
   }
-  const underscore = match[1];
-  return underscore + camelCase(str.substring(underscore.length));
+  return str.substring(0, prefixLength) + camelCase(str.substring(prefixLength));
 }
 
 function camelCaseKeys(obj) {

From cbd6a18c3706e5833505ba1bad7840153cbe4e74 Mon Sep 17 00:00:00 2001
From: segayuu <segayuu@gmail.com>
Date: Thu, 15 Nov 2018 11:33:52 +0900
Subject: [PATCH 4/4] Refactoring camelCaseKeys()

---
 lib/camel_case_keys.js | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/lib/camel_case_keys.js b/lib/camel_case_keys.js
index 557e4fe4..55e04f3e 100644
--- a/lib/camel_case_keys.js
+++ b/lib/camel_case_keys.js
@@ -29,18 +29,17 @@ function camelCaseKeys(obj) {
   if (typeof obj !== 'object') throw new TypeError('obj must be an object!');
 
   const keys = Object.keys(obj);
+  const { length } = keys;
   const result = {};
 
-  for (let i = 0, len = keys.length; i < len; i++) {
-    const key = keys[i];
-    const value = obj[key];
-    const newKey = toCamelCase(key);
+  for (let i = 0; i < length; i++) {
+    const oldKey = keys[i];
+    const newKey = toCamelCase(oldKey);
 
-    if (newKey === key) {
-      result[key] = value;
-    } else {
-      result[newKey] = value;
-      Object.defineProperty(result, key, {
+    result[newKey] = obj[oldKey];
+
+    if (newKey !== oldKey) {
+      Object.defineProperty(result, oldKey, {
         get: getter(newKey),
         set: setter(newKey),
         configurable: true,