Chart Component

A BookNest Chart Component Pattern

React 19 7,897 has no UMD build, so this build-free page imports ES modules from jsDelivr 15,886 and writes markup with htm templates (identical in JSX). jsDelivr's react-dom imports react@^19.3.0; importing react@19.3.0 separately loaded a second React and hooks failed ("reading 'useState'"), so the page uses that exact URL:

A React component: React renders the bars, D3 computes scales and draws one axis (sample data)HTML
<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>
<div id="root" style="font:12px Arial"></div>
<script type="module">
  const cdn = 'https://cdn.jsdelivr.net/npm/';           // react-dom imports react@^19.3.0,
  const React = (await import(`${cdn}react@%5E19.3.0/+esm`)).default;  // so use that same URL
  const { createRoot } = await import(`${cdn}react-dom@19.3.0/client/+esm`);
  const html = (await import(`${cdn}htm@3.1.1/+esm`)).default.bind(React.createElement);
  const { useMemo, useRef, useEffect } = React;
  function RatingsChart({ rows, width = 560, height = 150 }) {
    const x = useMemo(() => d3.scaleLinear([0, 5], [170, width - 30]), [width]);
    const y = useMemo(() => d3.scaleBand(rows.map(r => r.key), [0, height - 20]).padding(0.2),
      [rows, height]);
    const axis = useRef(null);
    useEffect(() => { d3.select(axis.current).call(d3.axisBottom(x).ticks(5)); }, [x]);
    return html`<svg width=${width} height=${height}>
      ${rows.map(r => html`<g key=${r.key} transform=${`translate(0,${y(r.key)})`}>
        <rect x=${x(0)} width=${x(r.mean) - x(0)} height=${y.bandwidth()} fill=${r.color} />
        <text x=${x(0) - 6} y=${y.bandwidth() / 2} dy="0.35em" text-anchor="end">
          ${r.title}</text>
      </g>`)}
      <g ref=${axis} transform=${`translate(0,${height - 20})`} />
    </svg>`;
  }
  const rows = prepareSales(SALES).ratings.map(r => ({ ...r.book,
    mean: d3.sum(r.counts, (c, i) => c * (i + 1)) / d3.sum(r.counts) }))
    .sort((a, b) => b.mean - a.mean);
  createRoot(document.getElementById('root')).render(html`<${RatingsChart} rows=${rows} />`);
  setTimeout(() => { window.__done = true; }, 300);          // after React's first commit
</script>
Browser output of Listing 6.55
Browser output of 55

useEffect draws the axis after React commits its <g>, and again only when the scale changes; hover would be plain React state. A real project bundles .jsx with Vite 25,978 (MERN Stack Development) and imports only the D3 18,089 modules it uses.

A React 19 RatingsChart component with htm: React renders the bars, D3 computes scales and draws the axisHTMLLive
<!doctype html>
<style>
  body { margin: 0; padding: 8px; background: #fafaf7; font: 12px system-ui, sans-serif; color: #263238; }
  #root svg { max-width: 100%; height: auto; }
</style>
<script src="https://cdn.jsdelivr.net/npm/d3@7.9.0/dist/d3.min.js"></script>
<!-- react-dom's CDN build imports react@^19.3.0: map every React URL to that one copy -->
<script type="importmap">
{ "imports": {
  "react": "https://cdn.jsdelivr.net/npm/react@%5E19.3.0/+esm",
  "react-dom/client": "https://cdn.jsdelivr.net/npm/react-dom@19.3.0/client/+esm",
  "htm": "https://cdn.jsdelivr.net/npm/htm@3.1.1/+esm",
  "https://cdn.jsdelivr.net/npm/react@19.3.0/+esm": "https://cdn.jsdelivr.net/npm/react@%5E19.3.0/+esm" } }
</script>
<div id="root"></div>
<script type="module">
  import React, { useMemo, useRef, useEffect, useState } from 'react';
  import { createRoot } from 'react-dom/client';
  import htm from 'htm';
  const html = htm.bind(React.createElement);           // tagged templates, identical in JSX

  // 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 };
  }

  function RatingsChart({ rows, width = 560, height = 170 }) {
    const [hover, setHover] = useState(null);           // hover is plain React state
    const x = useMemo(() => d3.scaleLinear([0, 5], [170, width - 40]), [width]);
    const y = useMemo(() => d3.scaleBand(rows.map(r => r.key), [0, height - 20]).padding(0.2), [rows, height]);
    const axis = useRef(null);
    // d3-axis must own its <g>: draw it after React commits, and again only when x changes
    useEffect(() => { d3.select(axis.current).call(d3.axisBottom(x).ticks(5)); }, [x]);
    return html`<svg width=${width} height=${height} font-size="12">
      ${rows.map(r => html`<g key=${r.key} transform=${`translate(0,${y(r.key)})`}
          onPointerEnter=${() => setHover(r.key)} onPointerLeave=${() => setHover(null)}>
        <rect x=${x(0)} width=${x(r.mean) - x(0)} height=${y.bandwidth()} fill=${r.color}
          opacity=${hover && hover !== r.key ? 0.3 : 1} />
        <text x=${x(0) - 6} y=${y.bandwidth() / 2} dy="0.35em" text-anchor="end">${r.title}</text>
        <text x=${x(r.mean) + 4} y=${y.bandwidth() / 2} dy="0.35em">${r.mean.toFixed(2)}</text>
      </g>`)}
      <g ref=${axis} transform=${`translate(0,${height - 20})`} />
    </svg>`;
  }
  const rows = prepareSales(SALES).ratings.map(r => ({ ...r.book,
    mean: d3.sum(r.counts, (c, i) => c * (i + 1)) / d3.sum(r.counts) })).sort((a, b) => b.mean - a.mean);
  createRoot(document.getElementById('root')).render(html`<${RatingsChart} rows=${rows} />`);
</script>