test: cover sliceFragment

src/config/constants.ts

@@ -1,5 +1,5 @@
 // detect device
-export const MOBILE = window.innerWidth < 600 || window.navigator.userAgentData?.mobile;
+export const MOBILE = globalThis.innerWidth < 600 || globalThis.navigator?.userAgentData?.mobile;
 
 // typed arrays max values
 export const INT8_MAX = 127;

src/utils/arrayUtils.test.ts

@@ -0,0 +1,29 @@
+import {describe, it, expect} from "vitest";
+
+import {sliceFragment} from "./arrayUtils";
+
+describe("sliceFragment", () => {
+  const array = ["a", "b", "c", "d", "e", "f"];
+
+  it("should return expected fragment within array length", () => {
+    expect(sliceFragment(array, 2, 2)).toEqual(["a", "b", "c", "d", "e"]);
+    expect(sliceFragment(array, 2, 1)).toEqual(["b", "c", "d"]);
+    expect(sliceFragment(array, 2, 0)).toEqual(["c"]);
+  });
+
+  it("should cycle array and return expected fragment if input is beyond array length", () => {
+    expect(sliceFragment(array, 1, 2)).toEqual(["f", "a", "b", "c", "d"]);
+    expect(sliceFragment(array, 0, 1)).toEqual(["f", "a", "b"]);
+    expect(sliceFragment(array, 5, 1)).toEqual(["e", "f", "a"]);
+  });
+
+  it("should return original array if boundaries exceed the array", () => {
+    expect(sliceFragment(array, 2, 10)).toEqual(array);
+    expect(sliceFragment([], 2, 10)).toEqual([]);
+  });
+
+  it("should throw an error if input is incorrect", () => {
+    expect(() => sliceFragment(array, -2, 2)).toThrow();
+    expect(() => sliceFragment(array, 2, -1)).toThrow();
+  });
+});

src/utils/arrayUtils.ts

@@ -1,4 +1,4 @@
-import {UINT16_MAX, UINT32_MAX, UINT8_MAX} from "../config/constants";
+import {UINT16_MAX, UINT32_MAX, UINT8_MAX} from "config/constants";
 
 export function last<T>(array: T[]) {
   return array[array.length - 1];
@@ -9,15 +9,18 @@ export function unique<T>(array: T[]) {
 }
 
 export function sliceFragment<T>(array: T[], index: number, zone: number) {
+  if (index < 0) throw new Error("Index must not be negative");
+  if (zone < 0) throw new Error("Zone must not be negative");
+
   if (zone + 1 + zone >= array.length) {
     return array.slice();
   }
 
   const start = index - zone;
-  const end = index + zone;
+  const end = index + zone + 1;
 
   if (start < 0) {
-    return array.slice(0, end).concat(array.slice(start));
+    return array.slice(start).concat(array.slice(0, end));
   }
 
   if (end >= array.length) {
@@ -27,8 +30,6 @@ export function sliceFragment<T>(array: T[], index: number, zone: number) {
   return array.slice(start, end);
 }
 
-window.sliceFragment = sliceFragment;
-
 interface ICreateTypesArrayLength {
   maxValue: number;
   length: number;