feat: add string truncate algorithm

String/Truncate.js

@@ -0,0 +1,23 @@
+/**
+ * @function truncate
+ * @description Truncates a string to a specified length and appends
+ *   an ellipsis (...) if the string exceeds that length.
+ * @param {string} str - The input string
+ * @param {number} maxLength - The maximum length of the output string
+ * @returns {string} - The truncated string
+ * @see https://en.wikipedia.org/wiki/Ellipsis
+ * @example truncate("Hello World", 5) => "Hello..."
+ * @example truncate("Hi", 5) => "Hi"
+ * @example truncate("Hello World", 11) => "Hello World"
+ */
+const truncate = (str, maxLength) => {
+  if (typeof str !== 'string') {
+    throw new TypeError('First argument must be a string')
+  }
+  if (!Number.isInteger(maxLength) || maxLength < 1) {
+    throw new TypeError('Second argument must be a positive integer')
+  }
+  return str.length > maxLength ? str.slice(0, maxLength) + '...' : str
+}
+
+export { truncate }

String/test/Truncate.test.js

@@ -0,0 +1,47 @@
+import { truncate } from '../Truncate.js'
+
+describe('truncate', () => {
+  test("truncate('Hello World', 5) returns 'Hello...'", () => {
+    expect(truncate('Hello World', 5)).toBe('Hello...')
+  })
+
+  test("truncate('Hi', 5) returns 'Hi'", () => {
+    expect(truncate('Hi', 5)).toBe('Hi')
+  })
+
+  test('truncate at exact length returns original', () => {
+    expect(truncate('Hello', 5)).toBe('Hello')
+  })
+
+  test("truncate('Hello World', 11) returns 'Hello World'", () => {
+    expect(truncate('Hello World', 11)).toBe('Hello World')
+  })
+
+  test('truncate empty string returns empty string', () => {
+    expect(truncate('', 5)).toBe('')
+  })
+
+  test('truncate with maxLength 1', () => {
+    expect(truncate('Hello', 1)).toBe('H...')
+  })
+
+  test('truncate long string', () => {
+    expect(truncate('The quick brown fox', 9)).toBe('The quick...')
+  })
+
+  test('throws TypeError for non-string input', () => {
+    expect(() => truncate(123, 5)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for zero maxLength', () => {
+    expect(() => truncate('Hello', 0)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for negative maxLength', () => {
+    expect(() => truncate('Hello', -1)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for float maxLength', () => {
+    expect(() => truncate('Hello', 2.5)).toThrow(TypeError)
+  })
+})