How do deep web crawlers handle JavaScript rendered content in web pages?

Deep web crawlers handle JavaScript-rendered content by executing JavaScript code in a headless browser environment before extracting data. This approach mimics how a real user interacts with a page, ensuring dynamic content is fully loaded before scraping.

Key Techniques:

1. Headless Browsers: Tools like Puppeteer or Selenium control a headless browser (e.g., Chrome) to render pages, execute scripts, and capture the final DOM.
2. Wait Strategies: Crawlers wait for specific elements to appear (e.g., via waitForSelector in Puppeteer) to ensure content is fully loaded.
3. API Interception: Some crawlers monitor network requests to directly fetch API responses that populate dynamic content, avoiding full page rendering.

Example:
A crawler targeting an e-commerce site with infinite scrolling loads the page in a headless browser, scrolls to the bottom to trigger AJAX calls, and extracts product data after all items are rendered.

For scalable solutions, Tencent Cloud's Web+, Serverless Cloud Function, and CDN acceleration can optimize crawling performance and handle large-scale JavaScript-heavy sites efficiently.