Added some tests and improved function

src/array/getClosestNumber.ts

@@ -13,6 +13,8 @@ export function getClosestNumberInArray(
   input: number,
   array: number[],
 ): number {
+  if (input === null || input === undefined || array.length < 1) return 0
+
   return array.reduce((a, b) =>
     Math.abs(b - input) < Math.abs(a - input) ? b : a,
   )

tests/array/closestNumber.test.ts

@@ -1,16 +1,31 @@
 import { describe, expect, it } from "vitest"
 import { getClosestNumberInArray } from "../../src"
-import { n } from "vitest/dist/reporters-2ff87305"
 
 describe("closestNumberInArray", () => {
   it("should return the closest value", () => {
 
 
     const data: [number, number[], number][] = [
+      [-100, [], 0],
+      [null, [10, 20], 0],
+      [undefined, [], 0],
+
+      [-1, [-100, 0, 0.25, 0.5, 0.75, 1], 0],
+      [-51, [-100, 0, 0.25, 0.5, 0.75, 1], -100],
       [0.2, [0, 0.25, 0.5, 0.75, 1], 0.25],
-      // TODO other examples
-      [0.2, [0, 0.25, 0.5, 0.75, 1], 0.25],
-      [0.2, [0, 0.25, 0.5, 0.75, 1], 0.25],
+
+      [-12, [-20, -10, 0, 10, 20], -10],
+      [-15, [-20, -10, 0, 10, 20], -20],
+      [-18, [-20, -10, 0, 10, 20], -20],
+      [0, [-20, -10, 0, 10, 20], 0],
+      [12, [-20, -10, 0, 10, 20], 10],
+      [15, [-20, -10, 0, 10, 20], 10],
+      [18, [-20, -10, 0, 10, 20], 20],
+
+      [375, [100, 200, 300, 400, 500], 400],
+      [-100, [100, 200, 300, 400, 500], 100],
+      [100, [-100, -200, -300, -400, -500], -100],
+      [-375, [-100, -200, -300, -400, -500], -400],
     ]
 
     for (let [input, array, result] of data) {