In this demo, we build a simple app that uses React and a simple Store object to load and display country data.


First, we pull in React, ReactDOM, and TinyBase:

<script src="/umd/react.production.min.js"></script>
<script src="/umd/react-dom.production.min.js"></script>
<script src="/umd/tinybase.js"></script>
<script src="/umd/ui-react.js"></script>

We import the functions and components we need:

const {
} = TinyBase;
const {
} = TinyBaseUiReact;
const {useCallback} = React;

We also set up some string constants for showing star emojis:

const STAR = '\u2605';
const UNSTAR = '\u2606';

Starting The App

We have a top-level App component, in which we initialize our data, and render the parts of the app. Firstly, we create and memoize a set of three Store objects:

  • countryStore contains a list of the world's countries, loaded once from a JSON file using a remote Persister object.
  • starStore contains a list of the countries that the user has starred. This is persisted to the browser's local storage and starts with eight default starred countries, persisted to local storage.
  • sessionStore contains the Id of an Indexes object, the Id of an index, and the Id of a slice, persisted to session storage. These three ids represent the 'current slice' view the user is looking at and we default the app to start showing the countries starting with the letter 'A'.
const App = () => {
  const countryStore = useCreateStore(() =>
      countries: {emoji: {type: 'string'}, name: {type: 'string'}},
    (store) =>
    async (persister) => await persister.load(),

  const starStore = useCreateStore(() =>
    createStore().setSchema({countries: {star: {type: 'boolean'}}}),
    (store) => createLocalPersister(store, 'countries/starStore'),
    async (persister) => {
      await persister.startAutoLoad({
        countries: {
          GB: {star: true},
          NZ: {star: true},
          AU: {star: true},
          SE: {star: true},
          IE: {star: true},
          IN: {star: true},
          BZ: {star: true},
          US: {star: true},
      await persister.startAutoSave();

  const sessionStore = useCreateStore(createStore);
    (store) => createSessionPersister(store, 'countries/sessionStore'),
    async (persister) => {
      await persister.startAutoLoad({
        ui: {
          currentSlice: {
            indexes: 'countryIndexes',
            indexId: 'firstLetter',
            sliceId: 'A',
      await persister.startAutoSave();
  // ...

We also create and memoize two Indexes objects with the useCreateIndexes hook:

  • countryIndexes contains a single Index of countries in countryStore by their first letter, sorted alphabetically.
  • starIndexes contains a single Index of the countries in starStore.

The code looks like this:

// ...
const countryIndexes = useCreateIndexes(countryStore, (store) =>
    (getCell) => getCell('name')[0],

const starIndexes = useCreateIndexes(starStore, (store) =>
  createIndexes(store).setIndexDefinition('star', 'countries', 'star'),
// ...

To start the app, we render the left-hand side Filter component and the main Countries component, wrapped in a Provider component that references the Store objects, and the Indexes objects:

  // ...
  return (
      storesById={{countryStore, starStore, sessionStore}}
      indexesById={{countryIndexes, starIndexes}}
      <Filters />
      <Countries />

We also use a simple grid layout to arrange the app:

@accentColor: #d81b60;
@spacing: 0.5rem;
@border: 1px solid #ccc;
@font-face {
  font-family: Lato;
  src: url(https://tinybase.org/fonts/lato-light.woff2) format('woff2');
body {
  box-sizing: border-box;
  display: flex;
  font-family: Lato, sans-serif;
  margin: 0;
  height: 100vh;
  padding: @spacing * 2;
  text-align: center;

Finally, when the window loads, we render the App component into the demo div to start the app:

window.addEventListener('load', () => ReactDOM.render(<App />, document.body));

The 'Current Slice'

At the heart of this app is the concept of the 'current slice': at any one time, the app is displaying the countries present in a specific sliceId of a specific indexId of a specific Indexes object. We store these three ids in the sessionStore object so they persist between reloads.

Since both the left-hand and right-hand panels of the app need to read these parameters, we provide a custom useCurrentSlice hook to get those three Cell values out of the currentSlice Row of the ui Table of the sessionStore:

const useCurrentSlice = () => useRow('ui', 'currentSlice', 'sessionStore');

When a user clicks on the letters on the left-hand side of the app, we need to write these values too. So we also provide a custom useSetCurrentSlice hook that provides a callback to set the three Cell values:

const useSetCurrentSlice = (indexes, indexId, sliceId) =>
    () => ({indexes, indexId, sliceId}),
    [indexes, indexId, sliceId],

The Filters Component

This component provides the list of countries' first letters down the left-hand side of the app. We actually build this as an IndexView component that lists all the sliceIds in the countryIndexes index, but also add an explicit item at the top of the list to allow the user to select starred countries from the starIndexes index.

The custom useCurrentSlice hook is used to get the current Indexes object name, current indexId, and current sliceId. We use these to determine whether a Filter is selected, and that flag is passed down as the selected prop to each of the child Filter components so they know whether to display themselves as selected or not. We could have each letter of the side bar listening for changes to the current slice, but in this case it is more efficient to do it once and pass down the currentSlice as a prop, using the getSliceComponentProps callback:

const Filters = () => {
  const {
    indexes: currentIndexes,
    indexId: currentIndexId,
    sliceId: currentSliceId,
  } = useCurrentSlice();

  return (
    <div id="filters">
          currentIndexes == 'starIndexes' &&
          currentIndexId == 'star' &&
          currentSliceId == 'true'
          (sliceId) => ({
              currentIndexes == 'countryIndexes' &&
              currentIndexId == 'firstLetter' &&
              currentSliceId == sliceId,
          [currentIndexes, currentIndexId, currentSliceId],

Each letter in the left hand Filters component is a Filter component, which knows which Indexes object the app needs to show, along with the index and slice Ids. This is set with the callback returned by the useSetCurrentSlice custom hook.

For example, clicking the letter 'N' will set the current named Indexes object to be countryIndexes, the current indexId to be firstLetter, and the current sliceId to be 'N'. Clicking the star at the to of the list will set the current named Indexes object to be starIndexes, the current indexId to be star, and the current sliceId to be 'true'.

The currentSlice prop passed down from the Filters component is used to decide whether to style the letter as the 'current' selection.

We also display the number of countries in the slice of the relevant index. Instead of setting up a Metrics object to track this, it's simpler to just use the useSliceRowIds hook and show the length of the resulting array. Only the count of starred countries changes during the life of the app anyway:

const Filter = ({
  indexes = 'countryIndexes',
  label = sliceId,
}) => {
  const handleClick = useSetCurrentSlice(indexes, indexId, sliceId);
  const className = 'filter' + (selected ? ' current' : '');
  const rowIdCount = useSliceRowIds(indexId, sliceId, indexes).length;

  return (
    <div className={className} onClick={handleClick}>
      <span className="label">{label}</span>
      <span className="count">{rowIdCount}</span>

These filters also have some straightforward styling:

#filters {
  overflow-y: scroll;
  border-right: @border;
  margin-right: @spacing;
  padding-right: @spacing;
  .filter {
    cursor: pointer;
    &.current {
      color: @accentColor;
    .count {
      display: inline-block;
      width: 2em;
    .count {
      color: #777;
      font-size: 0.8rem;
      text-align: left;

The Countries Component

The main right-hand side of the app is a panel that shows the view selected with the left-hand Filters component. As we have seen, that component is setting the 'current slice' to be shown, comprising the name of the Indexes object in focus, an indexId, and a sliceId. We use those three parameters directly as the props for the SliceView component that forms the main part of the app:

const Countries = () => (
  <div id="countries">
    <SliceView {...useCurrentSlice()} rowComponent={Country} />

Each Row that is present in the specified slice is a country, and the Country component renders a small panel for each.

As well as rendering the name and flag of the country (from the countryStore store), we also add a small 'star' at the top of each country panel. Clicking this will either call the setStar callback to favorite the country by adding it to the starStore, or it will call the setUnstar callback to unfavorite it and remove it again:

const Country = (props) => {
  const {tableId, rowId} = props;
  const star = useCell(tableId, rowId, 'star', 'starStore');
  const setStar = useSetCellCallback(
    () => true,
  const setUnstar = useDelCellCallback(
  const handleClick = star ? setUnstar : setStar;

  return (
    <div className="country">
      <div className="star" onClick={handleClick}>
        {star ? STAR : UNSTAR}
      <div className="flag">
        <CellView {...props} cellId="emoji" store="countryStore" />
      <div className="name">
        <CellView {...props} cellId="name" store="countryStore" />

Removing a country from the starStore store rather than setting the star flag to false prevents the starStore store from growing to include all the countries that were ever starred, even if no longer so. Since we are storing this in the browser, it's more efficient just to remove it.

The styling for the main panel of the app is a little more complex, but we want the country cards and flags to look good!

#countries {
  flex: 1;
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  grid-auto-rows: max-content;
  gap: @spacing;
  overflow-y: scroll;
  .country {
    background: #fff;
    border: @border;
    padding: @spacing;
    position: relative;
    height: fit-content;
    .star {
      cursor: pointer;
      display: inline;
      left: 8px;
      position: absolute;
      top: 5px;
      user-select: none;
    .flag {
      font-size: 5rem;
      line-height: 1em;
    .name {
      overflow: hidden;
      text-overflow: ellipsis;
      vertical-align: top;
      white-space: nowrap;

And that's it! A simple app, all in all, but one that demonstrates using Indexes objects and passing down props to build a useful stateful user interface.