What are the differences between Cheerio and Puppeteer? How to choose which one to use? - 面试题

Cheerio and Puppeteer are both tools for handling web pages in Node.js, but they have significant differences in design goals and use cases:

1. Core Differences

Feature	Cheerio	Puppeteer
Type	HTML Parser	Browser Automation Tool
JavaScript Execution	Not supported	Fully supported
Dynamic Content	Cannot handle	Fully supported
Performance	Extremely fast	Slower
Resource Consumption	Low	High
API	jQuery style	Browser DevTools Protocol
Use Cases	Static HTML parsing	Dynamic web pages, screenshots, PDF

2. Cheerio Characteristics

Advantages

Lightweight and fast: Core code is only a few hundred lines, extremely fast parsing
Simple and easy to use: jQuery-style API, low learning curve
Low resource consumption: No need to launch browser, low memory usage
Suitable for batch processing: Can quickly process large amounts of static pages

Limitations

Cannot execute JavaScript: Can only parse static HTML
Cannot handle dynamic content: Cannot get data loaded via JS
Cannot handle complex interactions: No support for clicking, scrolling, etc.
Cannot take screenshots or generate PDF: No visualization capabilities

Suitable Scenarios

javascript
// Suitable: Static web page data extraction
const cheerio = require('cheerio');
const axios = require('axios');

async function scrapeStaticSite() {
  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()
  };
}

3. Puppeteer Characteristics

Advantages

Complete browser environment: Uses real Chrome/Chromium
JavaScript execution: Can execute all JavaScript on the page
Dynamic content support: Can get AJAX-loaded data
Interactive capabilities: Supports clicking, input, scrolling, etc.
Visualization features: Supports screenshots, PDF generation
Network interception: Can monitor and modify network requests

Limitations

High resource consumption: Needs to launch complete browser instance
Slower speed: Much slower compared to Cheerio
High complexity: API is relatively complex, high learning curve
Difficult deployment: Complex to deploy in some server environments

Suitable Scenarios

javascript
// Suitable: Dynamic web pages, scenarios requiring interaction
const puppeteer = require('puppeteer');

async function scrapeDynamicSite() {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  
  await page.goto('https://example.com', { waitUntil: 'networkidle2' });
  
  // Wait for dynamic content to load
  await page.waitForSelector('.dynamic-content');
  
  const data = await page.evaluate(() => {
    return {
      title: document.title,
      content: document.querySelector('.dynamic-content').textContent
    };
  });
  
  await browser.close();
  return data;
}

4. Performance Comparison

javascript
// Cheerio - Fast parsing
const cheerio = require('cheerio');

async function cheerioBenchmark() {
  const start = Date.now();
  const $ = cheerio.load(htmlString);
  const items = $('.item').map((i, el) => $(el).text()).get();
  const time = Date.now() - start;
  
  console.log(`Cheerio: ${time}ms, ${items.length} items`);
  // Result: Usually < 10ms
}

// Puppeteer - Full browser
const puppeteer = require('puppeteer');

async function puppeteerBenchmark() {
  const start = Date.now();
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.setContent(htmlString);
  
  const items = await page.$$eval('.item', elements => 
    elements.map(el => el.textContent)
  );
  
  await browser.close();
  const time = Date.now() - start;
  
  console.log(`Puppeteer: ${time}ms, ${items.length} items`);
  // Result: Usually 500-2000ms
}

5. Selection Recommendations

Scenarios for Using Cheerio

Website content is static HTML
Need to process large amounts of pages
High performance requirements
Only need to extract data, no interaction needed
Limited server resources

Scenarios for Using Puppeteer

Website uses JavaScript to dynamically load content
Need to simulate user actions (clicking, scrolling, etc.)
Need screenshots or PDF generation
Need to handle complex SPA applications
Need to monitor network requests

Hybrid Usage Scenarios

javascript
// First use Puppeteer to get dynamic content, then use Cheerio to parse
const puppeteer = require('puppeteer');
const cheerio = require('cheerio');

async function hybridScrape() {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  
  // Use Puppeteer to load dynamic page
  await page.goto('https://example.com/dynamic');
  await page.waitForSelector('.content');
  
  // Get HTML
  const html = await page.content();
  await browser.close();
  
  // Use Cheerio to parse quickly
  const $ = cheerio.load(html);
  const data = $('.item').map((i, el) => ({
    title: $(el).find('.title').text(),
    content: $(el).find('.content').text()
  })).get();
  
  return data;
}

6. Practical Application Examples

Cheerio - Scraping Static Blog

javascript
async function scrapeBlog() {
  const response = await axios.get('https://blog.example.com');
  const $ = cheerio.load(response.data);
  
  return $('.post').map((i, el) => ({
    title: $(el).find('h2').text(),
    date: $(el).find('.date').text(),
    excerpt: $(el).find('.excerpt').text()
  })).get();
}

Puppeteer - Scraping Dynamic E-commerce Site

javascript
async function scrapeShop() {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  
  await page.goto('https://shop.example.com');
  
  // Scroll to load more products
  for (let i = 0; i < 5; i++) {
    await page.evaluate(() => window.scrollTo(0, document.body.scrollHeight));
    await page.waitForTimeout(1000);
  }
  
  const products = await page.$$eval('.product', items => 
    items.map(item => ({
      name: item.querySelector('.name').textContent,
      price: item.querySelector('.price').textContent
    }))
  );
  
  await browser.close();
  return products;
}

Summary

Cheerio: Suitable for static pages, high performance requirements, batch processing
Puppeteer: Suitable for dynamic pages, needs interaction, visualization requirements
Hybrid usage: Use Puppeteer to load dynamic content first, then use Cheerio to parse, can achieve the best balance of performance and functionality