Feat: Fibonacci Series

DIRECTORY.md

@@ -35,8 +35,10 @@
   * [Pronic Number](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/pronic_number.ts)
   * [Radians To Degrees](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/radians_to_degrees.ts)
   * Series
+    * [Fibonacci Numbers](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/series/fibonacci_numbers.ts)
     * [Hexagonal Numbers](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/series/hexagonal_numbers.ts)
     * Test
+      * [Fibonacci Numbers.Test](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/series/test/fibonacci_numbers.test.ts)
       * [Hexagonal Numbers.Test](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/series/test/hexagonal_numbers.test.ts)
   * [Sieve Of Eratosthenes](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/sieve_of_eratosthenes.ts)
   * [Signum](https://github.com/TheAlgorithms/TypeScript/blob/HEAD/maths/signum.ts)

maths/series/fibonacci_numbers.ts

@@ -0,0 +1,26 @@
+/**
+ * @function FibonacciNumbers
+ * @description To generate the requested number of fibonacci numbers
+ * @summary the Fibonacci sequence is a sequence in which each number is the sum of the two preceding ones.
+ * @see [Wikipedia](https://en.wikipedia.org/wiki/Fibonacci_sequence)
+ * @author MohdFaisalBidda <https://github.com/MohdFaisalBidda> 
+ * @param {number} n - The number of fibonacci numbers to generate
+ * @returns {number[]} - An array containing first 'n' fibonacci numbers
+ * @example fibonacciNumbers(7) = [ 0, 1, 1, 2, 3, 5, 8 ]
+ * @example fibonacciNumbers(15) =  [ 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377 ]
+ */
+export const FibonacciNumbers = (n: number): number[] => {
+    if (isNaN(n)) throw new Error('The input needs to be a number')
+    if (!Number.isInteger(n) || n < 0) throw new Error('The input needs to be a non-negative integer')  
+    if (n <= 0) return [];
+    if (n === 1) return [0];
+
+    const fibonacciNumbers: number[] = [0, 1];
+
+    while (fibonacciNumbers.length < n) {
+        const next = fibonacciNumbers[fibonacciNumbers.length - 1] + fibonacciNumbers[fibonacciNumbers.length - 2];
+        fibonacciNumbers.push(next);
+    }
+
+    return fibonacciNumbers;
+}

maths/series/test/fibonacci_numbers.test.ts

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+import { FibonacciNumbers } from "../fibonacci_numbers"; 
+
+describe("FibonacciNumbers", () => {
+  it("should return the first 10 fibonacci numbers", () => {
+    expect(FibonacciNumbers(10)).toStrictEqual([0, 1, 1, 2, 3, 5, 8, 13, 21, 34]);
+  })
+
+  it("should return the first 5 fibonacci numbers", () => {
+    expect(FibonacciNumbers(5)).toStrictEqual([0, 1, 1, 2, 3])
+  })
+
+  it("should return zero fibonacci numbers", () => {
+    expect(FibonacciNumbers(0)).toStrictEqual([])
+  })
+})