d3-shape and d3-geo generators accept a context: d3.line().context(ctx) and d3.geoPath(projection, ctx) call moveTo, lineTo and arc on it instead of returning a string, so you add only beginPath() and stroke(). Scale the backing store by devicePixelRatio (devicePixelRatio) for sharp lines:
<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>
<canvas width="620" height="140"></canvas>
<script>
const { months } = prepareSales(SALES), canvas = document.querySelector('canvas');
const dpr = window.devicePixelRatio || 1, W = 620, H = 140, ctx = canvas.getContext('2d');
canvas.width = W * dpr; canvas.height = H * dpr; canvas.style.width = `${W}px`;
ctx.scale(dpr, dpr); // draw in CSS pixels
const x = d3.scaleUtc(d3.extent(months, d => d.date), [30, W - 10]);
const y = d3.scaleLinear([0, 400], [H - 20, 10]);
const line = d3.line(d => x(d.date), d => y(d.units)).curve(d3.curveMonotoneX).context(ctx);
ctx.beginPath(); line(months); ctx.lineWidth = 2; ctx.strokeStyle = '#1f5f8b'; ctx.stroke();
ctx.font = '11px Arial'; // a hand-made axis
x.ticks(6).forEach(t => ctx.fillText(d3.utcFormat('%b %y')(t), x(t), H - 4));
y.ticks(4).forEach(v => ctx.fillText(v, 2, y(v) + 4));
</script>
Scales and generator are unchanged; only the output moved. You lose what the DOM gave for free: d3-axis cannot draw into a canvas, CSS cannot style marks, and hit-testing becomes your job (Hybrid Canvas-and-SVG Charts).
<!doctype html>
<style>
body { margin: 0; padding: 8px; background: #fafaf7; font: 12px system-ui, sans-serif; color: #263238; }
canvas { display: block; max-width: 100%; background: #fff; }
</style>
<script src="https://cdn.jsdelivr.net/npm/d3@7.9.0/dist/d3.min.js"></script>
<canvas></canvas>
<p id="out"></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 { months, sales } = prepareSales(SALES), canvas = document.querySelector('canvas');
const dpr = window.devicePixelRatio || 1, W = 600, H = 180, ctx = canvas.getContext('2d');
canvas.width = W * dpr; canvas.height = H * dpr; canvas.style.width = `${W}px`;
ctx.scale(dpr, dpr); // draw in CSS pixels, sharply
const x = d3.scaleUtc(d3.extent(months, d => d.date), [34, W - 10]);
const y = d3.scaleLinear([0, 130], [H - 20, 10]);
// Given a context, generators call moveTo/lineTo/bezierCurveTo on it instead of returning a string
for (const [book, rows] of d3.groups(sales, d => d.book)) { // one path per book
const line = d3.line(d => x(d.date), d => y(d.units)).curve(d3.curveMonotoneX).context(ctx);
ctx.beginPath(); line(rows);
ctx.lineWidth = 2; ctx.strokeStyle = book.color; ctx.stroke();
}
// d3.arc works the same way: a small donut of revenue share
const arc = d3.arc().innerRadius(14).outerRadius(26).context(ctx);
ctx.save(); ctx.translate(W - 50, 40);
for (const a of d3.pie().value(b => b.revenue)(d3.sort(new Set(sales.map(s => s.book)), b => b.id))) {
ctx.beginPath(); arc(a); ctx.fillStyle = a.data.color; ctx.fill();
}
ctx.restore();
// d3-axis cannot draw into a canvas: a hand-made axis from the scales' ticks
ctx.font = '11px system-ui'; ctx.fillStyle = '#546e7a';
x.ticks(6).forEach(t => ctx.fillText(d3.utcFormat('%b %y')(t), x(t) - 14, H - 4));
y.ticks(4).forEach(v => { ctx.fillText(v, 2, y(v) + 4); ctx.fillRect(30, y(v), W - 40, 0.5); });
document.getElementById('out').textContent = 'Scales and generators are unchanged; only the output moved from SVG to canvas.';
</script>