feat: add array unique algorithm

Data-Structures/Array/Unique.js

@@ -0,0 +1,19 @@
+/**
+ * @function unique
+ * @description Returns a new array with all duplicate values removed,
+ *   preserving the order of first occurrence.
+ * @param {Array} arr - The input array
+ * @returns {Array} - A new array with only unique values
+ * @see https://en.wikipedia.org/wiki/Set_(abstract_data_type)
+ * @example unique([1, 2, 2, 3]) => [1, 2, 3]
+ * @example unique([1, 1, 1]) => [1]
+ * @example unique([1, "1", 1]) => [1, "1"]
+ */
+const unique = (arr) => {
+  if (!Array.isArray(arr)) {
+    throw new TypeError('Input must be an array')
+  }
+  return [...new Set(arr)]
+}
+
+export { unique }

Data-Structures/Array/test/Unique.test.js

@@ -0,0 +1,45 @@
+import { unique } from '../Unique.js'
+
+describe('unique', () => {
+  test('unique([1, 2, 2, 3]) returns [1, 2, 3]', () => {
+    expect(unique([1, 2, 2, 3])).toEqual([1, 2, 3])
+  })
+
+  test('unique([1, 1, 1]) returns [1]', () => {
+    expect(unique([1, 1, 1])).toEqual([1])
+  })
+
+  test("unique([1, '1', 1]) returns [1, '1']", () => {
+    expect(unique([1, '1', 1])).toEqual([1, '1'])
+  })
+
+  test('unique([]) returns []', () => {
+    expect(unique([])).toEqual([])
+  })
+
+  test('unique with no duplicates returns same values', () => {
+    expect(unique([1, 2, 3])).toEqual([1, 2, 3])
+  })
+
+  test('unique preserves order of first occurrence', () => {
+    expect(unique([3, 1, 2, 1, 3])).toEqual([3, 1, 2])
+  })
+
+  test('unique works with strings', () => {
+    expect(unique(['a', 'b', 'a', 'c'])).toEqual(['a', 'b', 'c'])
+  })
+
+  test('unique does not mutate original array', () => {
+    const arr = [1, 2, 2, 3]
+    unique(arr)
+    expect(arr).toEqual([1, 2, 2, 3])
+  })
+
+  test('throws TypeError for non-array input', () => {
+    expect(() => unique('123')).toThrow(TypeError)
+  })
+
+  test('throws TypeError for null input', () => {
+    expect(() => unique(null)).toThrow(TypeError)
+  })
+})