fix(startCase): convert the non-first char to lowercase (#591)

* fix: convert the non-first char to lowercase

* test: more test case

* docs: update examples

docs/ja/reference/string/startCase.md

@@ -25,8 +25,8 @@ import { startCase } from 'es-toolkit/string';
 
 startCase('--foo-bar--'); // 'Foo Bar' を返します
 startCase('fooBar'); // 'Foo Bar' を返します
-startCase('__FOO_BAR__'); // 'FOO BAR' を返します
-startCase('XMLHttpRequest'); // 'XML Http Request' を返します
+startCase('__FOO_BAR__'); // 'Foo Bar' を返します
+startCase('XMLHttpRequest'); // 'Xml Http Request' を返します
 startCase('_abc_123_def'); // 'Abc 123 Def' を返します
 startCase('__abc__123__def__'); // 'Abc 123 Def' を返します
 startCase('_-_-_-_'); // '' を返します

docs/ko/reference/string/startCase.md

@@ -25,8 +25,8 @@ import { startCase } from 'es-toolkit/string';
 
 startCase('--foo-bar--'); // returns 'Foo Bar'
 startCase('fooBar'); // returns 'Foo Bar'
-startCase('__FOO_BAR__'); // returns 'FOO BAR'
-startCase('XMLHttpRequest'); // returns 'XML Http Request'
+startCase('__FOO_BAR__'); // returns 'Foo Bar'
+startCase('XMLHttpRequest'); // returns 'Xml Http Request'
 startCase('_abc_123_def'); // returns 'Abc 123 Def'
 startCase('__abc__123__def__'); // returns 'Abc 123 Def'
 startCase('_-_-_-_'); // returns ''

docs/reference/string/startCase.md

@@ -25,8 +25,8 @@ import { startCase } from 'es-toolkit/string';
 
 startCase('--foo-bar--'); // returns 'Foo Bar'
 startCase('fooBar'); // returns 'Foo Bar'
-startCase('__FOO_BAR__'); // returns 'FOO BAR'
-startCase('XMLHttpRequest'); // returns 'XML Http Request'
+startCase('__FOO_BAR__'); // returns 'Foo Bar'
+startCase('XMLHttpRequest'); // returns 'Xml Http Request'
 startCase('_abc_123_def'); // returns 'Abc 123 Def'
 startCase('__abc__123__def__'); // returns 'Abc 123 Def'
 startCase('_-_-_-_'); // returns ''

docs/zh_hans/reference/string/startCase.md

@@ -25,8 +25,8 @@ import { startCase } from 'es-toolkit/string';
 
 startCase('--foo-bar--'); // returns 'Foo Bar'
 startCase('fooBar'); // returns 'Foo Bar'
-startCase('__FOO_BAR__'); // returns 'FOO BAR'
-startCase('XMLHttpRequest'); // returns 'XML Http Request'
+startCase('__FOO_BAR__'); // returns 'Foo Bar'
+startCase('XMLHttpRequest'); // returns 'Xml Http Request'
 startCase('_abc_123_def'); // returns 'Abc 123 Def'
 startCase('__abc__123__def__'); // returns 'Abc 123 Def'
 startCase('_-_-_-_'); // returns ''

src/string/startCase.spec.ts

@@ -5,20 +5,20 @@ describe('startCase', function () {
   it('should capitalize each word', function () {
     expect(startCase('--foo-bar--')).toBe('Foo Bar');
     expect(startCase('fooBar')).toBe('Foo Bar');
-    expect(startCase('__FOO_BAR__')).toBe('FOO BAR');
+    expect(startCase('__FOO_BAR__')).toBe('Foo Bar');
   });
 
   it('should handle compound words', function () {
     expect(startCase('createElement')).toBe('Create Element');
     expect(startCase('iPhone')).toBe('I Phone');
-    expect(startCase('XMLHttpRequest')).toBe('XML Http Request');
+    expect(startCase('XMLHttpRequest')).toBe('Xml Http Request');
   });
 
   it('should handle various delimiters', function () {
     expect(startCase('_abc_123_def')).toBe('Abc 123 Def');
     expect(startCase('__abc__123__def__')).toBe('Abc 123 Def');
-    expect(startCase('ABC-DEF')).toBe('ABC DEF');
-    expect(startCase('ABC DEF')).toBe('ABC DEF');
+    expect(startCase('ABC-DEF')).toBe('Abc Def');
+    expect(startCase('ABC DEF')).toBe('Abc Def');
   });
 
   it('should handle empty strings', function () {
@@ -30,16 +30,16 @@ describe('startCase', function () {
   });
 
   it('should work with numbers', function () {
-    expect(startCase('12abc 12ABC')).toBe('12 Abc 12 ABC');
+    expect(startCase('12abc 12ABC')).toBe('12 Abc 12 Abc');
   });
 
   it('should handle consecutive uppercase letters', function () {
-    expect(startCase('ABC')).toBe('ABC');
-    expect(startCase('ABCdef')).toBe('AB Cdef');
+    expect(startCase('ABC')).toBe('Abc');
+    expect(startCase('ABCdef')).toBe('Ab Cdef');
   });
 
   it('should handle combinations of numbers and letters', function () {
-    expect(startCase('123ABC')).toBe('123 ABC');
+    expect(startCase('123ABC')).toBe('123 Abc');
     expect(startCase('a1B2c3')).toBe('A 1 B 2 C 3');
   });
 
@@ -58,4 +58,9 @@ describe('startCase', function () {
     expect(startCase('  foo  bar  ')).toBe('Foo Bar');
     expect(startCase('\tfoo\nbar')).toBe('Foo Bar');
   });
+
+  it('should convert the non-first characters to lowercase', function () {
+    expect(startCase('FOO BAR')).toBe('Foo Bar');
+    expect(startCase('FOO BAR BAZ')).toBe('Foo Bar Baz');
+  });
 });

src/string/startCase.ts

@@ -9,7 +9,7 @@ import { getWords } from './_internal/getWords.ts';
  *
  * @example
  * const result1 = startCase('hello world');  // result will be 'Hello World'
- * const result2 = startCase('HELLO WORLD');  // result will be 'HELLO WORLD'
+ * const result2 = startCase('HELLO WORLD');  // result will be 'Hello World'
  * const result3 = startCase('hello-world');  // result will be 'Hello World'
  * const result4 = startCase('hello_world');  // result will be 'Hello World'
  */
@@ -21,11 +21,8 @@ export function startCase(str: string): string {
     if (result) {
       result += ' ';
     }
-    if (word === word.toUpperCase()) {
-      result += word;
-    } else {
-      result += word[0].toUpperCase() + word.slice(1).toLowerCase();
-    }
+
+    result += word[0].toUpperCase() + word.slice(1).toLowerCase();
   }
   return result;
 }