d3.axisBottom(scale) (or axisTop, axisLeft, axisRight) returns a function that draws ticks into the <g> passed by call(): a path.domain plus a g.tick (a line and a text) per tick. ticks(), tickFormat() and tickSize() adjust it, and the output is plain SVG you can restyle. D3 18,089 has no legend module; a legend is a small join over the books:
<script src="https://cdn.jsdelivr.net/npm/d3@7.9.0/dist/d3.min.js"></script>
<script src="booknest-sales.js"></script>
<svg width="620" height="222" font-family="Arial" font-size="12"></svg>
<script>
const books = SALES.books.map(b => ({ ...b,
units: d3.sum(SALES.sales, s => s.book === b.id ? s.units : 0) }));
const x = d3.scaleLinear([10, 45], [50, 400]), y = d3.scaleLinear([0, 1400], [190, 10]);
const svg = d3.select('svg');
svg.append('g').attr('transform', 'translate(0,190)')
.call(d3.axisBottom(x).ticks(7).tickFormat(d => `$${d}`));
svg.append('g').attr('transform', 'translate(50,0)')
.call(d3.axisLeft(y).ticks(7).tickSize(-350)) // long ticks = gridlines
.call(g => g.select('.domain').remove())
.call(g => g.selectAll('.tick line').attr('stroke', '#ddd'));
svg.append('text').attr('x', 56).attr('y', 22).text('units (Jan 2025 to Aug 2026) by price');
svg.selectAll('circle').data(books).join('circle').attr('r', 8).attr('fill', d => d.color)
.attr('cx', d => x(d.price)).attr('cy', d => y(d.units));
const item = svg.append('g').attr('transform', 'translate(425, 40)').selectAll('g')
.data(books).join('g').attr('transform', (d, i) => `translate(0, ${i * 22})`);
item.append('rect').attr('width', 14).attr('height', 14).attr('fill', d => d.color);
item.append('text').attr('x', 20).attr('y', 12).text(d => d.title);
</script>
A negative tickSize() stretches the ticks into gridlines. A continuous color legend is a strip of rectangles (Color Scales) with an axis beneath it. The d3-svg-legend package (2.25.6) was last published in 2018 against D3 4-era modules, so hand-built legends are the norm; Observable Plot 40,840 draws them for you (Observable Plot).
<!doctype html>
<style>
body { margin: 0; padding: 8px; background: #fafaf7; font: 12px system-ui, sans-serif; color: #263238; }
svg { width: 100%; max-width: 600px; display: block; }
</style>
<script src="https://cdn.jsdelivr.net/npm/d3@7.9.0/dist/d3.min.js"></script>
<svg viewBox="0 0 600 222" font-size="12"></svg>
<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 };
})();
const books = SALES.books.map(b => ({ ...b,
units: d3.sum(SALES.sales, s => s.book === b.id ? s.units : 0) }));
const x = d3.scaleLinear([10, 45], [50, 380]), y = d3.scaleLinear([0, 1400], [190, 10]);
const svg = d3.select('svg');
svg.append('g').attr('transform', 'translate(0,190)')
.call(d3.axisBottom(x).ticks(7).tickFormat(d => `$${d}`));
svg.append('g').attr('transform', 'translate(50,0)')
.call(d3.axisLeft(y).ticks(7).tickSize(-330)) // long ticks become gridlines
.call(g => g.select('.domain').remove())
.call(g => g.selectAll('.tick line').attr('stroke', '#ddd'));
svg.append('text').attr('x', 56).attr('y', 22).text('units (Jan 2025 to Aug 2026) by price');
svg.selectAll('circle').data(books).join('circle').attr('r', 8).attr('fill', d => d.color)
.attr('cx', d => x(d.price)).attr('cy', d => y(d.units));
// D3 has no legend module: a legend is a small join over the books
const item = svg.append('g').attr('transform', 'translate(400, 40)').selectAll('g')
.data(books).join('g').attr('transform', (d, i) => `translate(0, ${i * 22})`);
item.append('rect').attr('width', 14).attr('height', 14).attr('fill', d => d.color);
item.append('text').attr('x', 20).attr('y', 12).text(d => d.title);
</script>