feat: add string repeat algorithm

String/RepeatString.js

@@ -0,0 +1,27 @@
+/**
+ * @function repeatString
+ * @description Repeats a string a specified number of times
+ *   without using JavaScript's built-in String.repeat().
+ * @param {string} str - The input string to repeat
+ * @param {number} n - Number of times to repeat
+ * @returns {string} - The repeated string
+ * @see https://en.wikipedia.org/wiki/String_(computer_science)
+ * @example repeatString("abc", 3) => "abcabcabc"
+ * @example repeatString("ha", 2) => "haha"
+ * @example repeatString("abc", 0) => ""
+ */
+const repeatString = (str, n) => {
+  if (typeof str !== 'string') {
+    throw new TypeError('First argument must be a string')
+  }
+  if (!Number.isInteger(n) || n < 0) {
+    throw new TypeError('Second argument must be a non-negative integer')
+  }
+  let result = ''
+  for (let i = 0; i < n; i++) {
+    result += str
+  }
+  return result
+}
+
+export { repeatString }

String/test/RepeatString.test.js

@@ -0,0 +1,43 @@
+import { repeatString } from '../RepeatString.js'
+
+describe('repeatString', () => {
+  test("repeatString('abc', 3) returns 'abcabcabc'", () => {
+    expect(repeatString('abc', 3)).toBe('abcabcabc')
+  })
+
+  test("repeatString('ha', 2) returns 'haha'", () => {
+    expect(repeatString('ha', 2)).toBe('haha')
+  })
+
+  test("repeatString('abc', 0) returns ''", () => {
+    expect(repeatString('abc', 0)).toBe('')
+  })
+
+  test("repeatString('abc', 1) returns 'abc'", () => {
+    expect(repeatString('abc', 1)).toBe('abc')
+  })
+
+  test('repeatString empty string returns empty string', () => {
+    expect(repeatString('', 5)).toBe('')
+  })
+
+  test('repeatString single char', () => {
+    expect(repeatString('a', 5)).toBe('aaaaa')
+  })
+
+  test('repeatString with spaces', () => {
+    expect(repeatString('ab ', 3)).toBe('ab ab ab ')
+  })
+
+  test('throws TypeError for non-string input', () => {
+    expect(() => repeatString(123, 3)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for negative n', () => {
+    expect(() => repeatString('abc', -1)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for float n', () => {
+    expect(() => repeatString('abc', 1.5)).toThrow(TypeError)
+  })
+})