add: get Nth Fibonacci algorithm implementation

Recursion/NthFibonacci.js

@@ -0,0 +1,27 @@
+/**
+ * Get the nth Fibonacci number.
+ *
+ * @param {number} n - The position of the Fibonacci number to find.
+ * @returns {number} - The nth Fibonacci number.
+ *
+ * @description
+ * The Fibonacci sequence is defined as follows: the first number of the sequence is 0, the second number is 1,
+ * and the nth number is the sum of the (n - 1)th and (n - 2)th numbers.
+ *
+ * For the purpose of this function, the first Fibonacci number is F0; therefore, getNthFib(1) is equal to F0,
+ * getNthFib(2) is equal to F1, and so on.
+ *
+ * The function uses a recursive approach to calculate the Fibonacci number for a given position.
+ *
+ * @Complexity
+ * The time complexity of this function is O(2^n), which makes it inefficient for large values of n.
+ * This is because it recalculates Fibonacci numbers multiple times for the same values.
+ */
+function getNthFib(n) {
+  if (n === 0) return 0;
+  if (n === 1) return 0;
+  if (n === 2) return 1;
+  return getNthFib(n - 1) + getNthFib(n - 2);
+}
+
+export { getNthFib };

Recursion/tests/NthFibonacci.test.js

@@ -0,0 +1,21 @@
+import { getNthFib } from "../NthFibonacci";
+
+describe("getNthFib", () => {
+  it("should return the correct Fibonacci number for a given position", () => {
+    expect(getNthFib(0)).toBe(0);
+    expect(getNthFib(1)).toBe(0);
+    expect(getNthFib(2)).toBe(1);
+    expect(getNthFib(3)).toBe(1);
+    expect(getNthFib(4)).toBe(2);
+    expect(getNthFib(5)).toBe(3);
+    expect(getNthFib(6)).toBe(5);
+    expect(getNthFib(7)).toBe(8);
+    expect(getNthFib(8)).toBe(13);
+    expect(getNthFib(9)).toBe(21);
+    expect(getNthFib(10)).toBe(34);
+    expect(getNthFib(15)).toBe(377);
+    expect(getNthFib(20)).toBe(4181);
+    expect(getNthFib(25)).toBe(46368);
+    expect(getNthFib(30)).toBe(514229);
+  });
+});