Averaging Dice Rolls

In this demo, we use a Metrics object to keep a count (and a rolling average) of the values in each Cell in a Store. We roll a dice 48 times and keep track of the average.

First, we create the import aliases for TinyBase and React modules we'll need:

<script type="importmap">
  {
    "imports": {
      "tinybase": "https://esm.sh/tinybase@6.4.0",
      "tinybase/ui-react": "https://esm.sh/tinybase@6.4.0/ui-react",
      "tinybase/ui-react-inspector": "https://esm.sh/tinybase@6.4.0/ui-react-inspector",
      "react": "https://esm.sh/react@^19.0.0",
      "react/jsx-runtime": "https://esm.sh/react@^19.0.0/jsx-runtime",
      "react-dom/client": "https://esm.sh/react-dom@^19.0.0/client"
    }
  }
</script>

We're using the Inspector component for the purposes of seeing how the data is structured.

We import the functions and components we need, and create the Store object:

import React from 'react';
import {createRoot} from 'react-dom/client';
import {createMetrics, createStore} from 'tinybase';
import {MetricView, Provider, TableView, useCell} from 'tinybase/ui-react';
import {Inspector} from 'tinybase/ui-react-inspector';

const store = createStore();

To create the Metrics object, we use the createMetrics function, and configure two definitions for it:

const metrics = createMetrics(store)
  .setMetricDefinition('average', 'rolls', 'avg', 'result')
  .setMetricDefinition('count', 'rolls', 'sum');

Each roll is going to be rendered as a dice Unicode character:

const Roll = ({tableId, rowId}) => (
  <span className="roll">
    {String.fromCharCode(9855 + useCell(tableId, rowId, 'result'))}
  </span>
);

The dice require a little styling:

.roll {
  display: inline-block;
  font-size: 3rem;
  padding: 0 1rem;
  line-height: 3rem;
}

We then create a React app comprising two MetricView components and a TableView component which will render the Roll components:

createRoot(document.body).render(
  <Provider store={store} metrics={metrics}>
    <p>
      Count: <MetricView metricId="count" />
      <br />
      Average: <MetricView metricId="average" />
    </p>
    <TableView tableId="rolls" rowComponent={Roll} />
    <Inspector />
  </Provider>,
);

We also added the Inspector component at the end there so you can inspect what is going on with the data during this demo. Simply click the TinyBase logo in the corner.

To roll the dice, we add a new Row every half second with the result, until the count of rolls reaches 48:

let rolls = 0;
const interval = setInterval(() => {
  if (rolls++ == 48) {
    clearInterval(interval);
  } else {
    store.addRow('rolls', {
      result: Math.ceil(Math.random() * 6),
    });
  }
}, 500);

Add a little styling, and we're done!

@font-face {
  font-family: Inter;
  src: url(https://tinybase.org/fonts/inter.woff2) format('woff2');
}

body {
  font-family: Inter, sans-serif;
  letter-spacing: -0.04rem;
  margin: 0;
}
p {
  margin: 1rem;
}

Next, we will use an IndexView component to group each Row of the Store object based on the value in a Cell within it. Please continue to the Grouping Dice Rolls demo.