What are the differences between Cheerio and jsdom? How to choose which one to use?

Cheerio and jsdom are both tools for handling HTML/XML in Node.js, but they have significant differences in design philosophy and implementation. Here's a detailed comparison:

1. Core Architecture Comparison

Cheerio

• Type: HTML Parser
• Underlying Implementation: Based on htmlparser2
• DOM Implementation: Custom lightweight DOM implementation
• JavaScript Execution: Not supported
• Browser Environment Simulation: Not simulated

jsdom

• Type: Complete DOM and browser environment simulator
• Underlying Implementation: Based on WHATWG DOM standard
• DOM Implementation: Complete W3C DOM specification implementation
• JavaScript Execution: Fully supported
• Browser Environment Simulation: Complete simulation

2. Feature Comparison Table

Feature	Cheerio	jsdom
HTML Parsing	✅ Fast	✅ Standard
CSS Selectors	✅ jQuery style	✅ Standard
DOM Manipulation	✅ Basic operations	✅ Complete API
JavaScript Execution	❌ Not supported	✅ Fully supported
Event Handling	❌ Not supported	✅ Fully supported
Performance	⚡ Extremely fast	🐢 Slower
Memory Usage	📉 Low	📈 High
Browser APIs	❌ None	✅ Complete
Network Requests	❌ None	✅ Supported
Canvas	❌ None	✅ Supported
LocalStorage	❌ None	✅ Supported

3. Usage Example Comparison

Cheerio Usage Example

javascript
const cheerio = require('cheerio');

const html = `
  <div id="container">
    <p class="text">Hello World</p>
    <button onclick="alert('Clicked')">Click</button>
  </div>
`;

const $ = cheerio.load(html);

// Basic operations
console.log($('#container').text()); // "Hello World"
console.log($('.text').text()); // "Hello World"

// DOM manipulation
$('.text').addClass('highlight');
console.log($('.text').attr('class')); // "text highlight"

// Cannot execute JavaScript
$('button').click(); // Invalid, Cheerio doesn't support events

jsdom Usage Example

javascript
const { JSDOM } = require('jsdom');

const html = `
  <div id="container">
    <p class="text">Hello World</p>
    <button onclick="alert('Clicked')">Click</button>
  </div>
`;

const dom = new JSDOM(html);
const document = dom.window.document;

// Basic operations
console.log(document.getElementById('container').textContent); // "Hello World"
console.log(document.querySelector('.text').textContent); // "Hello World"

// DOM manipulation
document.querySelector('.text').classList.add('highlight');
console.log(document.querySelector('.text').className); // "text highlight"

// Can execute JavaScript
const button = document.querySelector('button');
button.click(); // Valid, will trigger onclick event

// Can use browser APIs
console.log(dom.window.innerWidth); // Window width
console.log(dom.window.location.href); // Current URL

4. Performance Comparison

Parsing Speed Test

javascript
const cheerio = require('cheerio');
const { JSDOM } = require('jsdom');

const largeHtml = '<div>' + '<p>Test</p>'.repeat(10000) + '</div>';

// Cheerio performance test
const start1 = Date.now();
const $ = cheerio.load(largeHtml);
const cheerioTime = Date.now() - start1;
console.log(`Cheerio: ${cheerioTime}ms`);

// jsdom performance test
const start2 = Date.now();
const dom = new JSDOM(largeHtml);
const jsdomTime = Date.now() - start2;
console.log(`jsdom: ${jsdomTime}ms`);

// Typical results:
// Cheerio: 5-10ms
// jsdom: 100-500ms

Memory Usage Comparison

javascript
// Cheerio - Low memory usage
function cheerioMemoryTest() {
  const $ = cheerio.load(largeHtml);
  const elements = $('p');
  return elements.length;
}

// jsdom - High memory usage
function jsdomMemoryTest() {
  const dom = new JSDOM(largeHtml);
  const elements = dom.window.document.querySelectorAll('p');
  return elements.length;
}

5. Use Case Comparison

Scenarios for Using Cheerio

javascript
// 1. Web scraping and data extraction
async function scrapeWebsite() {
  const axios = require('axios');
  const response = await axios.get('https://example.com');
  const $ = cheerio.load(response.data);
  
  return {
    title: $('title').text(),
    links: $('a').map((i, el) => $(el).attr('href')).get()
  };
}

// 2. HTML content processing
function processHtml(html) {
  const $ = cheerio.load(html);
  $('script').remove(); // Remove scripts
  $('style').remove(); // Remove styles
  return $.html();
}

// 3. Batch processing large amounts of documents
function batchProcess(htmlList) {
  return htmlList.map(html => {
    const $ = cheerio.load(html);
    return $('title').text();
  });
}

Scenarios for Using jsdom

javascript
// 1. Testing frontend code
const { JSDOM } = require('jsdom');

function testFrontendCode() {
  const dom = new JSDOM(`
    <div id="app"></div>
    <script>
      document.getElementById('app').textContent = 'Hello';
    </script>
  `, { runScripts: 'dangerously' });
  
  console.log(dom.window.document.getElementById('app').textContent);
}

// 2. Server-side rendering (SSR)
function renderComponent(component) {
  const dom = new JSDOM('<div id="root"></div>');
  const root = dom.window.document.getElementById('root');
  
  // Execute component code
  component(root);
  
  return dom.serialize();
}

// 3. Processing content requiring JavaScript
function processDynamicContent(html) {
  const dom = new JSDOM(html, { 
    runScripts: 'dangerously',
    resources: 'usable' 
  });
  
  // Wait for JavaScript execution to complete
  return new Promise(resolve => {
    dom.window.onload = () => {
      resolve(dom.serialize());
    };
  });
}

6. API Comparison

Cheerio API Characteristics

javascript
const $ = cheerio.load(html);

// jQuery-style API
$('.class').text();
$('.class').html();
$('.class').attr('href');
$('.class').addClass('active');
$('.class').find('a');

// Chaining
$('.container')
  .find('.item')
  .addClass('highlight')
  .text();

// Unsupported browser APIs
$.window; // undefined
$.document; // undefined
$.localStorage; // undefined

jsdom API Characteristics

javascript
const dom = new JSDOM(html);
const document = dom.window.document;

// Standard DOM API
document.querySelector('.class').textContent;
document.querySelector('.class').innerHTML;
document.querySelector('.class').getAttribute('href');
document.querySelector('.class').classList.add('active');
document.querySelector('.class').querySelector('a');

// Supported browser APIs
dom.window.innerWidth;
dom.window.location.href;
dom.window.localStorage;
dom.window.fetch;
dom.window.console;

7. Selection Recommendations

Situations to Choose Cheerio

1. Only need to parse and extract data

   • Web scraping
   • Data extraction
   • HTML content processing

2. High performance requirements

   • Processing large amounts of documents
   • Batch operations
   • Real-time processing

3. Limited resources

   • Limited memory
   • Limited CPU
   • No server environment

4. Don't need browser features

   • Don't need to execute JavaScript
   • Don't need event handling
   • Don't need browser APIs

Situations to Choose jsdom

1. Need complete browser environment

   • Frontend code testing
   • Server-side rendering
   • Component testing

2. Need to execute JavaScript

   • Dynamic content processing
   • Client-side code execution
   • Framework rendering

3. Need browser APIs

   • LocalStorage
   • Fetch API
   • Canvas
   • Web Workers

4. Need standard DOM behavior

   • Event bubbling
   • DOM events
   • Browser compatibility testing

8. Hybrid Usage Scenarios

javascript
// First use jsdom to execute JavaScript, then use Cheerio to parse
const { JSDOM } = require('jsdom');
const cheerio = require('cheerio');

async function hybridProcess(html) {
  // 1. Use jsdom to execute JavaScript
  const dom = new JSDOM(html, { runScripts: 'dangerously' });
  
  // Wait for JavaScript execution
  await new Promise(resolve => {
    dom.window.onload = resolve;
  });
  
  // 2. Get HTML after execution
  const processedHtml = dom.serialize();
  
  // 3. Use Cheerio for fast parsing
  const $ = cheerio.load(processedHtml);
  
  return {
    title: $('title').text(),
    content: $('.content').text()
  };
}

Summary

• Cheerio: Lightweight, fast, focused on data extraction, suitable for scraping and static HTML processing
• jsdom: Complete, standard, simulates browser, suitable for testing and dynamic content processing
• Selection principle: Choose based on needs, use Cheerio for performance, use jsdom for complete functionality
• Hybrid usage: Can combine advantages of both, use jsdom to execute JS first, then use Cheerio to parse