simple and naive js object pagination implementation

paginate.js

const paginate = (array, pageSize) => {
  const numberOfPages = Math.round(array.length / pageSize);
  const needsOneMorePage = array.length % pageSize;
  
  const totalNumberOfPages = needsOneMorePage
    ? numberOfPages + 1
    : numberOfPages;

  const iterableNumberOfPages = [
    ...Array(totalNumberOfPages).keys()
  ];

  return iterableNumberOfPages.map((value, index) => {
    const startFromIndex = pageSize * index;
    const endIndex = startFromIndex + pageSize;
  
    return array.slice(startFromIndex, endIndex);
  })
}

module.exports = paginate;

paginate.test.js

const paginate = require('./paginate');

describe('paginate(arr, pageSize)', () => {
  it('should paginate array by 3 items per page', () => {
    const firstPage = [
      { id: 1 },
      { id: 2 },
      { id: 3 },
    ];

    const secondPage = [
      { id: 4 },
      { id: 5 },
      { id: 6 },
    ];

    const thirdPage = [
      { id: 7 },
      { id: 8 },
      { id: 9 },
    ];

    const lastPage = [
      { id: 10 },
    ];

    const items = [
        ...firstPage,
        ...secondPage,
        ...thirdPage,
        ...lastPage                
    ];

    const result = helpers.paginate(items, 3);

    expect(result.length).toEqual(4);
    expect(result[0]).toEqual(firstPage);
    expect(result[1]).toEqual(secondPage);
    expect(result[2]).toEqual(thirdPage);
    expect(result[3]).toEqual(lastPage);
  });
});