javascript 71 lines · 9 steps

A closure-based pagination helper in JS

A factory function keeps the current page private and exposes a small read/navigate API that the DOM renders against.

Explained by highlit

Intermediate closures encapsulation factory-function getters dom-rendering

1function usePagination(items, pageSize = 10) {
let currentPage = 1;
const totalPages = Math.max(1, Math.ceil(items.length / pageSize));
4 
function clamp(page) {
  return Math.min(Math.max(page, 1), totalPages);
}
8 
function slice() {
  const start = (currentPage - 1) * pageSize;
  return items.slice(start, start + pageSize);
}
13 
return {
  get page() {
    return currentPage;
  },
  get totalPages() {
    return totalPages;
  },
  get hasPrevious() {
    return currentPage > 1;
  },
  get hasNext() {
    return currentPage < totalPages;
  },
  get items() {
    return slice();
  },
  goTo(page) {
    currentPage = clamp(page);
    return slice();
  },
  next() {
    return this.goTo(currentPage + 1);
  },
  previous() {
    return this.goTo(currentPage - 1);
  },
};
41}
42 
43function renderControls(pager, container) {
container.innerHTML = `
  <button data-action="prev" ${pager.hasPrevious ? "" : "disabled"}>Previous</button>
  <span>Page ${pager.page} of ${pager.totalPages}</span>
  <button data-action="next" ${pager.hasNext ? "" : "disabled"}>Next</button>
`;
49 
container.querySelector('[data-action="prev"]').onclick = () => {
  pager.previous();
  renderList(pager);
  renderControls(pager, container);
};
container.querySelector('[data-action="next"]').onclick = () => {
  pager.next();
  renderList(pager);
  renderControls(pager, container);
};
60}
61 
62function renderList(pager) {
const list = document.getElementById("list");
list.replaceChildren(
  ...pager.items.map((item) => {
    const li = document.createElement("li");
    li.textContent = item.title;
    return li;
  })
);
71}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1A factory function plus closure hides mutable state behind a controlled, read-only surface.
2Getters let callers observe derived state like hasNext without exposing the underlying variable.
3Keeping navigation and rendering separate means the UI just reacts to whatever the pager reports.

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