feat: add title case algorithm

Author: sarthakgupta1907-cell

String/TitleCase.js

@@ -0,0 +1,23 @@
+/**
+ * @function titleCase
+ * @description Converts a string to title case where the first letter
+ *   of each word is capitalized and the rest are lowercase.
+ * @param {string} str - The input string
+ * @returns {string} - The title cased string
+ * @see https://en.wikipedia.org/wiki/Title_case
+ * @example titleCase("hello world") => "Hello World"
+ * @example titleCase("the quick brown fox") => "The Quick Brown Fox"
+ * @example titleCase("HELLO WORLD") => "Hello World"
+ */
+const titleCase = (str) => {
+  if (typeof str !== 'string') {
+    throw new TypeError('Input must be a string')
+  }
+  return str
+    .toLowerCase()
+    .split(' ')
+    .map((word) => word.charAt(0).toUpperCase() + word.slice(1))
+    .join(' ')
+}
+
+export { titleCase }

String/test/TitleCase.test.js

@@ -0,0 +1,39 @@
+import { titleCase } from '../TitleCase.js'
+
+describe('titleCase', () => {
+  test("titleCase('hello world') returns 'Hello World'", () => {
+    expect(titleCase('hello world')).toBe('Hello World')
+  })
+
+  test("titleCase('the quick brown fox') returns 'The Quick Brown Fox'", () => {
+    expect(titleCase('the quick brown fox')).toBe('The Quick Brown Fox')
+  })
+
+  test("titleCase('HELLO WORLD') returns 'Hello World'", () => {
+    expect(titleCase('HELLO WORLD')).toBe('Hello World')
+  })
+
+  test("titleCase('') returns ''", () => {
+    expect(titleCase('')).toBe('')
+  })
+
+  test('titleCase single word', () => {
+    expect(titleCase('javascript')).toBe('Javascript')
+  })
+
+  test('titleCase handles multiple spaces', () => {
+    expect(titleCase('hello  world')).toBe('Hello  World')
+  })
+
+  test('titleCase handles mixed case', () => {
+    expect(titleCase('hElLo WoRlD')).toBe('Hello World')
+  })
+
+  test('throws TypeError for non-string input', () => {
+    expect(() => titleCase(123)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for null', () => {
+    expect(() => titleCase(null)).toThrow(TypeError)
+  })
+})