The roving tabindex pattern makes the chart one tab stop: only the current bar has tabindex="0", arrow keys, Home and End move focus inside, and an aria-live region announces each value. A script focuses the first bar, then presses ArrowDown and End:
<script src="https://cdn.jsdelivr.net/npm/d3@7.9.0/dist/d3.min.js"></script>
<script src="booknest-sales.js"></script><script src="booknest-prep.js"></script>
<script src="booknest-a11y.js"></script>
<style>g:focus { outline: none } g:focus rect { stroke: #263238; stroke-width: 3 }</style>
<h3 id="chart-title" style="font:14px Arial;margin:0">Mean star rating per book</h3>
<p id="chart-summary" style="font:12px Arial;margin:0">Salt and Saffron rates highest.</p>
<svg width="560" height="150" font-family="Arial" font-size="12"></svg>
<p id="live" aria-live="polite" style="font:12px Arial;margin:4px 0"></p>
<script>
const bars = accessibleRatings(d3.select('svg'), prepareSales(SALES).ratings);
const nodes = bars.nodes();
bars.attr('tabindex', (d, i) => i === 0 ? 0 : -1)
.on('focus', event => d3.select('#live').text(event.currentTarget.ariaLabel))
.on('keydown', event => {
const i = nodes.indexOf(event.currentTarget), last = nodes.length - 1;
const next = { ArrowDown: i + 1, ArrowUp: i - 1, Home: 0, End: last }[event.key];
if (next === undefined) return; // let Tab and other keys through
event.preventDefault(); // no page scrolling
const target = nodes[Math.max(0, Math.min(last, next))];
nodes.forEach(n => n.setAttribute('tabindex', n === target ? 0 : -1));
target.focus();
});
nodes[0].focus(); // simulate ArrowDown, then End
for (const key of ['ArrowDown', 'End']) document.activeElement
.dispatchEvent(new KeyboardEvent('keydown', { key, bubbles: true }));
window.__done = true;
</script>
Focus moved through The Quiet Harbor to the last bar. Append marks in reading order, since focus follows the DOM, and draw a visible focus stroke, since SVG ignores most outlines.
<!doctype html>
<style>
body { margin: 0; padding: 8px; background: #fafaf7; font: 12px system-ui, sans-serif; color: #263238; }
svg { width: 100%; max-width: 560px; display: block; }
g:focus { outline: none; }
g:focus rect { stroke: #263238; stroke-width: 3; } /* SVG ignores most outlines: draw one */
h3 { font-size: 14px; margin: 0; }
</style>
<script src="https://cdn.jsdelivr.net/npm/d3@7.9.0/dist/d3.min.js"></script>
<h3 id="chart-title">Mean star rating per book</h3>
<p id="chart-summary" style="margin:0">Salt and Saffron rates highest. Tab into the chart, then use ↑ ↓ Home End.</p>
<svg viewBox="0 0 560 150" font-size="12"></svg>
<p id="live" aria-live="polite" style="font-weight:bold"></p>
<script>
// BookNest sample data, invented for these examples (not real sales)
const SALES = (() => {
const books = [
{ id: 1, key: 'harbor', title: 'The Quiet Harbor', author: 'Elena Marsh', genre: 'Fiction', color: '#1f5f8b', price: 18.99, rating: 4.6 },
{ id: 2, key: 'deepweb', title: 'Patterns of the Deep Web', author: 'Ravi Menon', genre: 'Technology', color: '#5b3f99', price: 39.5, rating: 4.3 },
{ id: 3, key: 'saffron', title: 'Salt and Saffron', author: 'Leila Haddad', genre: 'Cooking', color: '#e09a10', price: 24, rating: 4.8 },
{ id: 4, key: 'summit', title: 'Small Steps to Big Summits', author: 'Tom Okafor', genre: 'Self-Help', color: '#3f7d3a', price: 14.99, rating: 4.1 },
{ id: 5, key: 'clock', title: "The Clockmaker's Paradox", author: 'Iris Vale', genre: 'Science Fiction', color: '#b5452f', price: 16.2, rating: 4.5 },
{ id: 6, key: 'glass', title: 'Gardens in Glass', author: 'June Park', genre: 'Gardening', color: '#2a9d8f', price: 22.5, rating: 4.4 },
];
const units = { // units sold per month, January 2025 to August 2026
1: [40, 47, 46, 47, 57, 51, 46, 54, 60, 60, 71, 111, 52, 42, 49, 56, 59, 48, 53, 51],
2: [40, 37, 35, 41, 48, 43, 40, 42, 50, 53, 53, 84, 42, 35, 38, 41, 45, 41, 46, 46],
3: [46, 45, 41, 46, 53, 49, 46, 45, 60, 51, 63, 100, 48, 48, 49, 48, 53, 49, 48, 52],
4: [100, 80, 72, 70, 66, 66], // released March 2026
5: [48, 47, 54, 52, 65, 55, 57, 58, 64, 66, 75, 124, 58, 49, 59, 56, 63, 57, 54, 57],
6: [31, 30, 28, 35, 31, 32, 29, 30, 41, 36, 45, 64, 31, 30, 30, 38, 40, 38, 36, 38],
};
const months = d3.utcMonths(new Date('2025-01-01'), new Date('2026-09-01')).map(d3.utcFormat('%Y-%m'));
const sales = books.flatMap(b => units[b.id].map((n, i) =>
({ month: months[i + months.length - units[b.id].length], book: b.id, units: n })));
const ratings = [[4, 8, 20, 87, 293], [6, 10, 22, 95, 147], [2, 3, 8, 45, 342], [2, 3, 8, 24, 28],
[4, 8, 20, 90, 228], [4, 7, 20, 82, 147]].map((counts, i) => ({ book: i + 1, counts })); // 1 to 5 stars
const regions = [{ id: '826', name: 'United Kingdom', units: 1480 }, { id: '276', name: 'Germany', units: 1120 },
{ id: '250', name: 'France', units: 760 }, { id: '372', name: 'Ireland', units: 540 },
{ id: '528', name: 'Netherlands', units: 410 }, { id: '724', name: 'Spain', units: 320 }];
const links = [[5, 1, 38], [1, 3, 24], [2, 5, 18], [3, 6, 21], [4, 1, 12], [2, 6, 9], [4, 3, 15], [5, 6, 14]]
.map(([source, target, value]) => ({ source, target, value })); // customers who bought both
return { books, sales, ratings, regions, links };
})();
// prepareSales(raw): parsed dates, sales linked to book objects, revenue and totals
function prepareSales(raw) {
const parse = d3.utcParse('%Y-%m'), books = raw.books.map(b => ({ ...b }));
const byId = d3.index(books, b => b.id);
const sales = raw.sales.map(s => ({ date: parse(s.month), book: byId.get(s.book),
units: s.units, revenue: s.units * byId.get(s.book).price }));
for (const [book, rows] of d3.group(sales, s => s.book)) {
book.units = d3.sum(rows, s => s.units);
book.revenue = d3.sum(rows, s => s.revenue);
}
const months = d3.rollups(sales, v => ({ units: d3.sum(v, s => s.units),
revenue: d3.sum(v, s => s.revenue) }), s => +s.date).map(([t, v]) => ({ date: new Date(t), ...v }))
.sort((a, b) => a.date - b.date);
const ratings = raw.ratings.map(r => ({ ...r, book: byId.get(r.book) }));
return { ...raw, books, sales, months, ratings };
}
const rows = prepareSales(SALES).ratings.map(r => ({ ...r.book, n: d3.sum(r.counts),
mean: d3.sum(r.counts, (c, i) => c * (i + 1)) / d3.sum(r.counts) })).sort((a, b) => b.mean - a.mean);
const y = d3.scaleBand(rows.map(r => r.title), [4, 146]).padding(0.2), x = d3.scaleLinear([0, 5], [170, 500]);
const svg = d3.select('svg').attr('role', 'group').attr('aria-labelledby', 'chart-title chart-summary');
// Marks appended in reading order, since focus follows the DOM
const bars = svg.append('g').attr('role', 'list').selectAll('g').data(rows).join('g').attr('role', 'listitem')
.attr('aria-label', r => `${r.title}: ${r.mean.toFixed(2)} stars from ${r.n} reviews`)
.attr('transform', r => `translate(0,${y(r.title)})`);
bars.append('rect').attr('x', x(0)).attr('width', r => x(r.mean) - x(0)).attr('height', y.bandwidth()).attr('fill', r => r.color);
bars.append('text').attr('x', x(0) - 6).attr('y', y.bandwidth() / 2).attr('dy', '0.35em').attr('text-anchor', 'end')
.attr('aria-hidden', 'true').text(r => r.title);
const nodes = bars.nodes();
bars.attr('tabindex', (d, i) => i === 0 ? 0 : -1) // only the current bar is a tab stop
.on('focus', event => d3.select('#live').text(event.currentTarget.getAttribute('aria-label')))
.on('keydown', event => {
const i = nodes.indexOf(event.currentTarget), last = nodes.length - 1;
const next = { ArrowDown: i + 1, ArrowUp: i - 1, Home: 0, End: last }[event.key];
if (next === undefined) return; // let Tab and other keys through
event.preventDefault(); // no page scrolling
const target = nodes[Math.max(0, Math.min(last, next))];
nodes.forEach(n => n.setAttribute('tabindex', n === target ? 0 : -1));
target.focus();
});
// Simulate: focus the first bar, then press ArrowDown twice
nodes[0].focus({ preventScroll: true });
for (const key of ['ArrowDown', 'ArrowDown'])
document.activeElement.dispatchEvent(new KeyboardEvent('keydown', { key, bubbles: true }));
</script>