Chartjs Overview

Chart.js Overview (v4.5.1)

Guidance for installing, configuring, and optimizing Chart.js v4.5.1 in web applications.

Installation

npm Installation

Install Chart.js via npm:

npm install chart.js

CDN Installation

Include Chart.js via CDN in HTML:

<!-- jsDelivr -->
<script src="https://cdn.jsdelivr.net/npm/chart.js"></script>

<!-- CDNJS -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/4.5.1/chart.umd.min.js"></script>

Basic Chart Creation

Create a chart with minimal configuration:

<div>
  <canvas id="myChart"></canvas>
</div>

<script src="https://cdn.jsdelivr.net/npm/chart.js"></script>
<script>
  const ctx = document.getElementById('myChart');

  new Chart(ctx, {
    type: 'bar',
    data: {
      labels: ['Red', 'Blue', 'Yellow', 'Green', 'Purple', 'Orange'],
      datasets: [{
        label: '# of Votes',
        data: [12, 19, 3, 5, 2, 3],
        borderWidth: 1
      }]
    },
    options: {
      scales: {
        y: {
          beginAtZero: true
        }
      }
    }
  });
</script>

Key requirements:

• A <canvas> element with an id
• Wrap canvas in a container <div> for responsive sizing
• Instantiate new Chart(ctx, config) with type, data, and options

Module Bundlers (Webpack, Rollup, Vite, Parcel)

Quick Start (All Components)

Import everything for rapid prototyping:

import Chart from 'chart.js/auto';

new Chart(ctx, {
  type: 'bar',
  data: { /* ... */ }
});

Warning: chart.js/auto disables tree-shaking. Use manual registration for production.

Bundle Optimization (Tree-Shaking)

Register only needed components for smaller bundles:

import {
  Chart,
  BarController,
  BarElement,
  CategoryScale,
  LinearScale,
  Legend,
  Tooltip
} from 'chart.js';

Chart.register(
  BarController,
  BarElement,
  CategoryScale,
  LinearScale,
  Legend,
  Tooltip
);

new Chart(ctx, {
  type: 'bar',
  data: { /* ... */ }
});

See references/tree-shaking.md for complete component lists per chart type.

Module Loader Support

CommonJS

Use dynamic import in CommonJS modules:

const { Chart } = await import('chart.js');

RequireJS (AMD)

Require the UMD build:

require(['path/to/chartjs/dist/chart.umd.min.js'], function(Chart) {
  const myChart = new Chart(ctx, { /* ... */ });
});

ES Modules (Script Tag)

Use type="module" with ESM CDN for modern browsers:

<script type="module">
  import Chart from 'https://cdn.jsdelivr.net/npm/chart.js/+esm';

  new Chart(ctx, {
    type: 'bar',
    data: { /* ... */ }
  });
</script>

Tree-shaking with ES Modules:

<script type="module">
  import {
    Chart,
    BarController,
    BarElement,
    CategoryScale,
    LinearScale
  } from 'https://cdn.jsdelivr.net/npm/chart.js/+esm';

  Chart.register(BarController, BarElement, CategoryScale, LinearScale);

  new Chart(ctx, {
    type: 'bar',
    data: { /* ... */ }
  });
</script>

See examples/production-bundle.html for complete working examples.

Configuration Structure

Every Chart.js configuration follows this structure:

const config = {
  type: 'line',           // Chart type
  data: {                 // Data and datasets
    labels: [],
    datasets: [{ data: [] }]
  },
  options: {},            // Chart options
  plugins: []             // Inline plugins
};

new Chart(ctx, config);

Global Configuration

Set defaults for all charts using Chart.defaults:

// Set font defaults globally
Chart.defaults.font.family = "'Inter', sans-serif";
Chart.defaults.font.size = 14;

// Set interaction mode globally
Chart.defaults.interaction.mode = 'nearest';
Chart.defaults.interaction.intersect = false;

// Set default for all line charts
Chart.defaults.datasets.line.showLine = false;
Chart.defaults.datasets.line.tension = 0.4;

// Set default for linear scales
Chart.defaults.scales.linear.min = 0;

// Plugin defaults
Chart.defaults.plugins.legend.position = 'bottom';
Chart.defaults.plugins.tooltip.backgroundColor = 'rgba(0, 0, 0, 0.8)';

Important: Changes to Chart.defaults only affect charts created after the change.

See references/configuration-patterns.md for advanced global configuration patterns.

Helper Functions

Import helpers separately from the helpers package for event handling and utilities:

import Chart from 'chart.js/auto';
import { getRelativePosition } from 'chart.js/helpers';

const chart = new Chart(ctx, {
  type: 'line',
  data: data,
  options: {
    onClick: (e) => {
      // Convert event position to chart coordinates
      const canvasPosition = getRelativePosition(e, chart);

      // Get data values at click position
      const dataX = chart.scales.x.getValueForPixel(canvasPosition.x);
      const dataY = chart.scales.y.getValueForPixel(canvasPosition.y);

      console.log(`Clicked at: (${dataX}, ${dataY})`);
    }
  }
});

Available helpers: getRelativePosition, isNullOrUndef, isArray, isObject, valueOrDefault, uid

See references/configuration-patterns.md for complete helper function reference.

Chart Instance Methods

Common methods available on chart instances for dynamic updates and manipulation:

const chart = new Chart(ctx, config);

// Update chart with new data
chart.data.datasets[0].data = [1, 2, 3, 4, 5];
chart.update();              // Default animation
chart.update('none');        // No animation (faster)
chart.update('active');      // Only active elements animate

// Resize chart
chart.resize();              // Auto-detect from container
chart.resize(800, 400);      // Set specific dimensions

// Reset to original state
chart.reset();

// Destroy chart instance (important for cleanup)
chart.destroy();

// Export chart as image
const image = chart.toBase64Image();                    // PNG
const jpeg = chart.toBase64Image('image/jpeg', 0.8);   // JPEG 80% quality

// Get elements at event position
const elements = chart.getElementsAtEventForMode(
  event,
  'nearest',
  { intersect: true },
  true
);

// Toggle dataset visibility
chart.hide(datasetIndex);
chart.show(datasetIndex);
chart.isDatasetVisible(datasetIndex);

Performance tip: Use update('none') for frequent updates to disable animation.

See references/instance-methods.md for complete method documentation and patterns.

Responsiveness

Charts are responsive by default, automatically resizing with their container:

new Chart(ctx, {
  type: 'bar',
  data: data,
  options: {
    responsive: true,           // Resize with container (default: true)
    maintainAspectRatio: true,  // Keep aspect ratio (default: true)
    aspectRatio: 2,             // Width/height ratio (default: 2, radial: 1)
    resizeDelay: 0,             // Debounce resize updates in ms (default: 0)

    // Callback when chart resizes
    onResize: (chart, size) => {
      console.log(`Resized to ${size.width}x${size.height}`);
    }
  }
});

Container-based sizing: Chart.js gets dimensions from the canvas's parent container:

<div style="width: 80%; max-width: 1200px;">
  <canvas id="myChart"></canvas>
</div>

Flexbox/Grid containers: Set min-width: 0 on flex/grid children to prevent overflow:

<div style="display: grid; grid-template-columns: 1fr 1fr;">
  <div style="min-width: 0;"><canvas id="chart1"></canvas></div>
  <div style="min-width: 0;"><canvas id="chart2"></canvas></div>
</div>

Custom aspect ratios:

options: {
  aspectRatio: 1    // Square (radar, polar area)
  aspectRatio: 3    // Wide (timelines)
  aspectRatio: 0.5  // Tall (rankings)
}

Fixed-size charts:

options: {
  responsive: false,
  maintainAspectRatio: false
}

<canvas id="myChart" width="600" height="400"></canvas>

See references/configuration-patterns.md for responsive patterns and media query-like behavior.

Additional Resources

Reference Documentation:

• references/tree-shaking.md - Complete component registration guide for all chart types
• references/instance-methods.md - Chart instance methods, animation modes, and patterns
• references/configuration-patterns.md - Global defaults, helpers, responsive patterns

Working Examples:

• examples/basic-bar-chart.html - Bar chart examples (simple, horizontal, stacked)
• examples/multi-dataset-line.html - Multi-dataset and area charts with real-time updates
• examples/production-bundle.html - Tree-shaken builds with ESM imports