Debugging tools and techniques

Debugging Tools and Techniques

ECharts, as a powerful data visualization library, inevitably presents various issues during development. Efficient debugging tools and techniques can significantly improve development efficiency, helping to quickly locate and resolve problems.

Browser Developer Tools

Built-in browser developer tools are the foundation for debugging ECharts charts. Chrome DevTools' Elements panel allows inspection of the chart's DOM structure, while the Console panel outputs logs and error messages.

// Insert console.log in the code to check data
console.log('Chart data:', option.series[0].data);

The Network panel monitors data requests to ensure the API returns the correct data format. The Sources panel allows setting breakpoints to step through code and observe variable changes.

ECharts Instance Inspection

Use the getOption method to retrieve the current chart configuration and compare it with the expected configuration:

const chartInstance = echarts.init(document.getElementById('chart'));
console.log('Current options:', chartInstance.getOption());

Use getDataURL to export the chart as an image and verify the rendering result:

const imgData = chartInstance.getDataURL({
  type: 'png',
  pixelRatio: 2
});
console.log(imgData); // Output base64 image data

Error Handling and Capture

ECharts provides an error event listening mechanism:

chartInstance.on('error', function(error) {
  console.error('ECharts error:', error);
});

For asynchronous data loading, handle potential exceptions:

fetch('/api/data')
  .then(response => response.json())
  .then(data => {
    chartInstance.setOption(updateOption(data));
  })
  .catch(error => {
    console.error('Data loading failed:', error);
    chartInstance.showLoading('error', {
      text: 'Data loading failed',
      color: '#ff4500'
    });
  });

Performance Analysis Tools

Use Chrome's Performance panel to record the chart rendering process:

1. Click the Record button
2. Perform chart operations (initialization, data updates, etc.)
3. Stop recording and analyze the flame chart

Focus on:

• Long Scripting time may indicate inefficient data processing logic
• Long Rendering time may suggest overly complex chart configurations

Responsive Debugging Techniques

When debugging responsive layouts, listen for window size changes:

window.addEventListener('resize', function() {
  chartInstance.resize();
  console.log('New container size:', {
    width: document.getElementById('chart').offsetWidth,
    height: document.getElementById('chart').offsetHeight
  });
});

When using ECharts' media query feature, print the currently applied configuration:

chartInstance.on('media', function(params) {
  console.log('Media query triggered:', params);
});

Data Validation Techniques

For complex data transformations, validate step by step:

// Raw data
const rawData = [...];
console.log('Raw data length:', rawData.length);

// First processing step
const processedStep1 = rawData.map(item => ({...}));
console.log('After first step:', processedStep1.slice(0, 3));

// Final processing
const finalData = transformData(processedStep1);
console.log('Final data structure:', {
  dimensions: Object.keys(finalData[0]),
  sample: finalData[0]
});

Visual Debugging Methods

Temporarily modify styles to quickly locate issues:

// Highlight all axis labels
chartInstance.setOption({
  xAxis: {
    axisLabel: {
      backgroundColor: 'rgba(255,0,0,0.2)'
    }
  }
});

// Show borders for all data points
chartInstance.setOption({
  series: [{
    itemStyle: {
      borderColor: '#000',
      borderWidth: 1
    }
  }]
});

Debugging Complex Animations

For animation issues, adjust the duration for easier observation:

chartInstance.setOption({
  animationDuration: 3000, // Extend animation time
  animationEasing: 'linear' // Use linear animation for easier observation
});

Use animation event hooks:

chartInstance.on('finished', function() {
  console.log('Animation complete');
});

Server-Side Rendering Debugging

Compare differences when using SVG or Canvas renderers:

// Force Canvas renderer
const chartInstance = echarts.init(
  document.getElementById('chart'),
  null,
  { renderer: 'canvas' }
);

// Force SVG renderer
const chartInstance = echarts.init(
  document.getElementById('chart'),
  null,
  { renderer: 'svg' }
);

Memory Leak Detection

For long-running pages, monitor memory issues:

// Clean up before destruction
window.addEventListener('beforeunload', function() {
  chartInstance.dispose();
});

// Periodically check memory
setInterval(function() {
  console.log('Memory usage:', performance.memory);
}, 10000);

Cross-Browser Debugging

Address differences in browser behavior:

// Detect current browser
console.log('UserAgent:', navigator.userAgent);

// Browser feature detection
console.log('Canvas support:', !!document.createElement('canvas').getContext);
console.log('SVG support:', !!document.createElementNS);

Theme Debugging

Validate effects when applying custom themes:

// Register theme
echarts.registerTheme('custom', {
  color: ['#c12e34', '#e6b600', '#0098d9']
});

// Apply theme
const chartInstance = echarts.init(
  document.getElementById('chart'),
  'custom'
);

Accessibility Debugging

Check if ARIA attributes are correctly applied:

const ariaElements = document.querySelectorAll('[aria-label]');
ariaElements.forEach(el => {
  console.log('ARIA element:', el, 'Label:', el.getAttribute('aria-label'));
});