npm install puppeteer

const puppeteer = require('puppeteer');
 
(async () => {
  const browser = await puppeteer.launch({
    headless: false
  });
  const page = await browser.newPage();
  await page.goto('https://www.cnblogs.com/morethink/p/6525216.html');
  await page.setViewport({
    width: 1200,
    height: 800
  });
 
  await autoScroll(page);
 
  await page.screenshot({
    path: '1.png',
    fullPage: true
  });
 
  await browser.close();
})();
 
 
function autoScroll(page) {
  return page.evaluate(() => {
    return new Promise((resolve, reject) => {
      var totalHeight = 0;
      var distance = 100;
      var timer = setInterval(() => {
        var scrollHeight = document.body.scrollHeight;
        window.scrollBy(0, distance);
        totalHeight += distance;
        if (totalHeight >= scrollHeight) {
          clearInterval(timer);
          resolve();
        }
      }, 100);
    })
  });
}

const puppeteer = require('puppeteer');
 
(async () => {
  const browser = await puppeteer.launch({
    headless: false
  });
  const page = await browser.newPage();
  await page.goto('https://www.cnblogs.com/morethink/p/6525216.html');
  await page.setViewport({
    width: 1200,
    height: 800
  });
  //获取页面Dom对象
  let body = await page.$('#cnblogs_post_body');
  //调用页面内Dom对象的 screenshot 方法进行截图
  await body.screenshot({
    path: '2.png'
  });
  await browser.close();
})();