fix(utils): 특수 문자에 대한 개수와 공백에 대한 처리 추가 (#168)

* fix(utils): 특수 문자에 대한 개수와 공백에 대한 처리 추가

* chore: console.log 제거

* refactor(utils): 함수 배치 수정 및 while 문 가독성 향상

* docs(utils): 중복 문자열에 대한 옵션 허용 문서화

docs/docs/utils/string/countSubstringOccurrences.md

@@ -19,4 +19,8 @@ import { countSubstringOccurrences } from '@modern-kit/utils';
 const str = 'apple banana apple grapes apple';
 const count1 = countSubstringOccurrences(str, 'apple'); // 3
 const count2 = countSubstringOccurrences(str, 'apple banana'); // 1
+
+const duplicatedStr = 'aaaa'
+const count3 = countSubstringOccurrences(duplicatedStr, 'aa'); // 2, double counting not allowed
+const count4 = countSubstringOccurrences(duplicatedStr, 'aa', { overlap: true }); // 3, double counting allowed
 ```

packages/utils/src/string/countSubstringOccurrences/countSubstringOccurrences.spec.ts

@@ -16,4 +16,20 @@ describe('countSubstringOccurrences', () => {
     expect(countSubstringOccurrences(str2, '테스트')).toBe(4);
     expect(countSubstringOccurrences(str2, '테스트용 문자열')).toBe(2);
   });
+
+  it('should return 0 when either source or target is an empty string', () => {
+    expect(countSubstringOccurrences('', 'abc')).toBe(0);
+    expect(countSubstringOccurrences('abc', '')).toBe(0);
+  });
+
+  it('should return the correct count of occurrences', () => {
+    expect(countSubstringOccurrences('abc', 'abc')).toBe(1);
+    expect(countSubstringOccurrences('aaaa', 'aa', { overlap: true })).toBe(3);
+    expect(countSubstringOccurrences('banana', 'na')).toBe(2);
+  });
+
+  it('should handle special characters in the target string', () => {
+    expect(countSubstringOccurrences('a.b.c', '.')).toBe(2);
+    expect(countSubstringOccurrences('a(b)c(d)e', '(')).toBe(2);
+  });
 });

packages/utils/src/string/countSubstringOccurrences/index.ts

@@ -1,6 +1,39 @@
-export const countSubstringOccurrences = (source: string, target: string) => {
-  const regex = new RegExp(target, 'g');
-  const matches = source.match(regex);
+type Options = { overlap: boolean };
+
+const escapeRegExp = (str: string): string => {
+  return str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+};
+
+const countAllowOverlap = (source: string, regex: RegExp) => {
+  let count = 0;
+  let match = regex.exec(source);
 
+  while (match !== null) {
+    count++;
+    regex.lastIndex = match.index + 1;
+
+    match = regex.exec(source);
+  }
+
+  return count;
+};
+
+const countExceptOverlap = (source: string, regex: RegExp) => {
+  const matches = source.match(regex);
   return matches ? matches.length : 0;
 };
+
+export const countSubstringOccurrences = (
+  source: string,
+  target: string,
+  options: Options = { overlap: false }
+): number => {
+  if (target === '') return 0;
+
+  const escapedTarget = escapeRegExp(target);
+  const regex = new RegExp(escapedTarget, 'g');
+
+  return options.overlap
+    ? countAllowOverlap(source, regex)
+    : countExceptOverlap(source, regex);
+};