js_widget

A Flutter package that allows you to use any JavaScript-based widget as a Flutter widget through webview integration. This library is heavily inspired by and re-uses the awesome work that high_chart has done. I just made it generic for any JS widget instead of just highchart.

Features

• 🚀 Cross-platform support: Works on both web and mobile platforms
• 🔧 Generic implementation: Use any JavaScript widget, not just charts
• 📱 Webview integration: Seamless integration with Flutter webview
• 🎨 Customizable: Support for custom loaders, scripts, and event listeners
• 📐 Flexible sizing: Configurable widget dimensions
• 🔌 Event handling: Listen to JavaScript events from your widgets

Getting started

Installation

Add this to your package's pubspec.yaml file:

dependencies:
  js_widget: ^0.0.1

Import

import 'package:js_widget/js_widget.dart';

Usage

Basic Example

JsWidget(
  id: 'my-chart',
  size: const Size(400, 300),
  createHtmlTag: () => 'div',
  scriptToInstantiate: () => 'new Chart(ctx, config)',
  data: '{"labels": ["A", "B", "C"], "datasets": [{"data": [1, 2, 3]}]}',
  scripts: [
    'https://cdn.jsdelivr.net/npm/chart.js',
  ],
)

Advanced Example with Custom Loader and Event Listener

JsWidget(
  id: 'advanced-chart',
  size: const Size(600, 400),
  createHtmlTag: () => 'canvas',
  scriptToInstantiate: () => '''
    const ctx = document.getElementById('advanced-chart');
    const chart = new Chart(ctx, {
      type: 'line',
      data: $data,
      options: {
        responsive: true,
        interaction: {
          mode: 'index',
          intersect: false,
        },
      }
    });
    
    // Listen for chart events
    chart.canvas.addEventListener('click', function(evt) {
      const points = chart.getElementsAtEventForMode(evt, 'nearest', {intersect: true}, true);
      if (points.length) {
        const firstPoint = points[0];
        const label = chart.data.labels[firstPoint.index];
        const value = chart.data.datasets[firstPoint.datasetIndex].data[firstPoint.index];
        window.flutter_inappwebview.callHandler('chartClick', label, value);
      }
    });
  ''',
  data: jsonEncode(chartData),
  scripts: [
    'https://cdn.jsdelivr.net/npm/chart.js',
  ],
  loader: const Center(
    child: Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        CircularProgressIndicator(),
        SizedBox(height: 16),
        Text('Loading chart...'),
      ],
    ),
  ),
  listener: (String message) {
    print('Received message from JS: $message');
  },
)

API Reference

JsWidget

The main widget class that renders JavaScript widgets.

Constructor Parameters

Parameter	Type	Required	Description
id	String	Yes	Unique identifier for the widget
size	Size	Yes	Dimensions of the widget (width × height)
createHtmlTag	Function	Yes	Function that returns the HTML tag to create
scriptToInstantiate	Function	Yes	Function that returns the JavaScript code to instantiate the widget
data	String	Yes	Data to pass to the JavaScript widget
loader	Widget	No	Widget to show while loading (defaults to CircularProgressIndicator)
scripts	List<String>	No	List of JavaScript files to load
listener	Function(String)?	No	Callback function for JavaScript messages
preCreateScript	Function?	No	Function that returns JavaScript code to run before widget creation

Methods

• evalScript(String script): Execute JavaScript code in the webview context

Platform Support

• ✅ Web: Full support using dart:html
• ✅ Android: Full support using webview_flutter
• ✅ iOS: Full support using webview_flutter
• ❌ Desktop: Limited support (shows unsupported platform message)

Examples

Check out the example/ directory for complete working examples:

• Chart.js Integration: See how to integrate Chart.js for beautiful charts
• Custom Widgets: Learn how to create custom JavaScript widgets

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Inspired by high_chart
• Built with Flutter and Dart
• Uses webview_flutter for mobile support

Issues and Feedback

Please file issues and feature requests on the GitHub repository.