How to paginate Cloud Firestore data with ReactJs

Question

I'm working with Firebase - Cloud Firestore and at the moment I would like to paginate all the records available. I already have a list of records and what is left is some pagination for this. I'm new with Cloud Firestore, so any clarity is appreciated.

I checked the Firestore documentation (https://firebase.google.com/docs/firestore/query-data/query-cursors#paginate_a_query) and examples with ReactJS, but there is not much available.

I understand that eg:.startAt(0), .limit(10), but the question is how to paginate properly with this component called at the render method.

import React, { Component } from 'react';
import Pagination from "react-js-pagination";
import firestore from "./Firebase";

export default class DataList extends Component {

constructor(props) {
    super(props);
    this.state = {
        dbItems: [],
        currentPage: 1,
        itemsPerPage: 3,
        totalItemCount: 1,
        activePage: 15
    }
    this.handlePageChange = this.handlePageChange.bind(this);
}

handlePageChange(pageNumber) {
    console.log(`active page is ${pageNumber}`);
    this.setState({ activePage: pageNumber });
}

async getItems() {
    const { currentPage, itemsPerPage } = this.state;
    const startAt = currentPage * itemsPerPage - itemsPerPage;
    const usersQuery = firestore.collection('Users').orderBy("email").startAt(startAt).limit(itemsPerPage)
    const snapshot = await usersQuery.get()
    const items = snapshot.docs.map(doc => doc.data())
    return this.setState({ 
        dbItems: items,
        totalItemCount: firestore.collection('Users').get().then(res => console.log(res.size))
    })

}

componentDidMount() {
    this.getItems()
}

componentDidUpdate(prevProps, prevState) {
    const isDifferentPage = this.state.currentPage !== prevState.currentPage
    if (isDifferentPage) this.getItems()
}

render() {
    return (
        <div>
            {this.state.dbItems.map((users, index) => {
                return (
                    <p key={index}>
                        <b>First Name:</b> {users.firstname} <br />
                        <b>Email:</b> {users.email}
                    </p>
                )
            })
            }
            <Pagination
                activePage={this.state.activePage}
                itemsCountPerPage={this.state.itemsPerPage}
                totalItemsCount={this.state.totalItemCount}
                pageRangeDisplayed={this.state.itemsPerPage}
                onChange={this.handlePageChange}
            />
        </div>
    )
}
}

Thank you for the help!

Answer 1

Pagination can be achieved using startAt()

// Get Items.
async fetchUsers = () => {

  // State.
  const {users, usersPerPage} = this.state

  // Last Visible.
  const lastVisible = users && users.docs[users.docs.length - 1]

  // Query.
  const query = firestore.collection('Users')
    .orderBy('email')
    .startAfter(lastVisible)
    .limit(usersPerPage)

  // Users.
  const users = await query.get()

  // ..
  return this.setState({users})

}

// Did Mount.
componentDidMount() {
  this.fetchUsers()
}

// Did Update.
componentDidUpdate(prevProps, prevState) {
  const isDifferentPage = this.state.currentPage !== prevState.currentPage
  if (isDifferentPage) this.fetchUsers()
}