feat(lowerCase): Add lowerCase function (#166)

* feat(lowerCase): Add lowerCase function

* Update docs/ko/reference/string/lowerCase.md

* Update docs/ko/reference/string/lowerCase.md

* Update docs/reference/string/lowerCase.md

Co-authored-by: Evan Moon <bboydart91@gmail.com>

---------

Co-authored-by: Sojin Park <raon0211@gmail.com>
Co-authored-by: Evan Moon <bboydart91@gmail.com>
Co-authored-by: Sojin Park <raon0211@toss.im>

benchmarks/lowerCase.bench.ts

@@ -0,0 +1,15 @@
+import { bench, describe } from 'vitest';
+import { lowerCase as lowerCaseToolkit } from 'es-toolkit';
+import { lowerCase as lowerCaseLodash } from 'lodash';
+
+describe('lowerCase', () => {
+  bench('es-toolkit/lowerCase', () => {
+    const str = 'camelCase';
+    lowerCaseToolkit(str);
+  });
+
+  bench('lodash/lowerCase', () => {
+    const str = 'camelCase';
+    lowerCaseLodash(str);
+  });
+});

docs/.vitepress/en.mts

@@ -149,6 +149,7 @@ function sidebar(): DefaultTheme.Sidebar {
           items: [
             { text: 'snakeCase', link: '/reference/string/snakeCase' },
             { text: 'kebabCase', link: '/reference/string/kebabCase' },
+            { text: 'lowerCase', link: '/reference/string/lowerCase' },
             { text: 'capitalize', link: '/reference/string/capitalize' },
           ],
         },

docs/.vitepress/ko.mts

@@ -148,6 +148,7 @@ function sidebar(): DefaultTheme.Sidebar {
           items: [
             { text: 'snakeCase', link: '/ko/reference/string/snakeCase' },
             { text: 'kebabCase', link: '/ko/reference/string/kebabCase' },
+            { text: 'lowerCase', link: '/ko/reference/string/lowerCase' },
             { text: 'capitalize', link: '/ko/reference/string/capitalize' },
           ],
         },

docs/ko/reference/string/lowerCase.md

@@ -0,0 +1,30 @@
+# lowerCase
+
+문자열을 소문자 표기법으로 변환해요.
+
+소문자 표기법은 여러 단어로 구성된 식별자의 각 단어를 소문자로 쓰고, 단어를 공백( )으로 연결하는 명명 규칙입니다. 예를 들어 `lower case`처럼 써요.
+
+## 인터페이스
+
+```typescript
+function lowerCase(str: string): string;
+```
+
+### 파라미터
+
+- `str` (`string`): 소문자로 변환할 문자열이에요.
+
+### 반환 값
+
+(`string`) 소문자로 변환된 문자열이에요.
+
+## 예시
+
+```typescript
+import { lowerCase } from 'es-toolkit/string';
+
+lowerCase('camelCase'); // returns 'camel case'
+lowerCase('some whitespace'); // returns 'some whitespace'
+lowerCase('hyphen-text'); // returns 'hyphen text'
+lowerCase('HTTPRequest'); // returns 'http request'
+```

docs/reference/string/lowerCase.md

@@ -0,0 +1,30 @@
+# lowerCase
+
+Converts a string to lower case.
+
+Lower case is the naming convention in which each word is written in lowercase and separated by an space ( ) character. For example, `lower case`.
+
+## Signature
+
+```typescript
+function lowerCase(str: string): string;
+```
+
+### Parameters
+
+- `str` (`string`): The string that is to be changed to lower case.
+
+### Returns
+
+(`string`) The converted string to lower case.
+
+## Examples
+
+```typescript
+import { lowerCase } from 'es-toolkit/string';
+
+lowerCase('camelCase'); // returns 'camel case'
+lowerCase('some whitespace'); // returns 'some whitespace'
+lowerCase('hyphen-text'); // returns 'hyphen text'
+lowerCase('HTTPRequest'); // returns 'http request'
+```

src/string/index.ts

@@ -1,3 +1,4 @@
 export { snakeCase } from './snakeCase.ts';
 export { kebabCase } from './kebabCase.ts';
+export { lowerCase } from './lowerCase.ts';
 export { capitalize } from './capitalize.ts';

src/string/lowerCase.spec.ts

@@ -0,0 +1,40 @@
+import { describe, it, expect } from 'vitest';
+import { lowerCase } from './lowerCase';
+
+describe('lowerCase', () => {
+  it('should change camel case to lower case', async () => {
+    expect(lowerCase('camelCase')).toEqual('camel case');
+  });
+
+  it('should change space to space', async () => {
+    expect(lowerCase('some whitespace')).toEqual('some whitespace');
+  });
+
+  it('should change hyphen to space', async () => {
+    expect(lowerCase('hyphen-text')).toEqual('hyphen text');
+  });
+
+  it('should change Acronyms to small letter', async () => {
+    expect(lowerCase('HTTPRequest')).toEqual('http request');
+  });
+
+  it('should handle leading and trailing whitespace', async () => {
+    expect(lowerCase('    leading and trailing whitespace')).toEqual('leading and trailing whitespace');
+  });
+
+  it('should handle special characters correctly', async () => {
+    expect(lowerCase('special@characters!')).toEqual('special characters');
+  });
+
+  it('should handle strings that are already in lower case', async () => {
+    expect(lowerCase('lower_case')).toEqual('lower case');
+  });
+
+  it('should work with an empty string', async () => {
+    expect(lowerCase('')).toEqual('');
+  });
+
+  it('should work with screaming snake case', async () => {
+    expect(lowerCase('FOO_BAR')).toEqual('foo bar');
+  });
+});

src/string/lowerCase.ts

@@ -0,0 +1,21 @@
+import { CASE_SPLIT_PATTERN } from '../constants';
+
+/**
+ * Converts a string to lower case.
+ *
+ * Lower case is the naming convention in which each word is written in lowercase and separated by an space ( ) character.
+ *
+ * @param {string} str - The string that is to be changed to lower case.
+ * @returns {string} - The converted string to lower case.
+ *
+ * @example
+ * const convertedStr1 = lowerCase('camelCase') // returns 'camel case'
+ * const convertedStr2 = lowerCase('some whitespace') // returns 'some whitespace'
+ * const convertedStr3 = lowerCase('hyphen-text') // returns 'hyphen text'
+ * const convertedStr4 = lowerCase('HTTPRequest') // returns 'http request'
+ */
+
+export const lowerCase = (str: string): string => {
+  const splitWords = str.match(CASE_SPLIT_PATTERN) || [];
+  return splitWords.map(word => word.toLowerCase()).join(' ');
+};