@vectara/vectara-ui/lib/components/table/createPagination.test.js

Vectara's design system, codified as a React and Sass component library

import { createPagination } from "./createPagination";
describe("createPagination", () => {
    describe("when numPages <= 5", () => {
        test("returns page numbers if numPages === 5", () => {
            expect(createPagination(1, 5)).toEqual({ items: [1, 2, 3, 4, 5], activeIndex: 0 });
        });
        test("returns page numbers if numPages < 5", () => {
            expect(createPagination(3, 3)).toEqual({ items: [1, 2, 3], activeIndex: 2 });
        });
    });
    describe("when numPages > 5", () => {
        describe("and page is within 2 pages of the first and last page", () => {
            test("truncates last couples pages when on page 1", () => {
                expect(createPagination(1, 6)).toEqual({ items: [1, 2, 3, "...", 6], activeIndex: 0 });
            });
            test("truncates last couples pages when on page 2", () => {
                expect(createPagination(2, 6)).toEqual({ items: [1, 2, 3, "...", 6], activeIndex: 1 });
            });
            test("truncates first couples pages when on page 4", () => {
                expect(createPagination(4, 6)).toEqual({ items: [1, "...", 4, 5, 6], activeIndex: 2 });
            });
            test("truncates first couples pages when on page 5", () => {
                expect(createPagination(5, 6)).toEqual({ items: [1, "...", 4, 5, 6], activeIndex: 3 });
            });
        });
        describe("and page is beyond 2 pages of the first and last page", () => {
            test("truncates frist and last couples pages", () => {
                expect(createPagination(15, 50)).toEqual({ items: [1, "...", 15, "...", 50], activeIndex: 2 });
            });
        });
    });
});