Pupperteer Tutorial

  1. 1. What is Pupperteer
  2. 2. Usage
    1. 2.1 General
  3. 3. Learn by doing
    1. 3.1 See an example to learn how the thing works
    2. 3.2 crawlsite.js

This post is merely some notes when I learnt pupperteer, basically contain similar info from google developer webpage. Try to organize those info in a personal understandable way here.

1. What is Pupperteer

Most thins you can do manually in the browser now can be done with puppeteer.

2. Usage

2.1 General

  • Create an instance of Browser
  • Open pages
  • manipulate them with Puppeteer’s API

3. Learn by doing

3.1 See an example to learn how the thing works

/**
 * Copyright 2018 Google Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @author ebidel@ (Eric Bidelman)
 */

/**
 * Takes a screenshot of the latest tweet in a user's timeline and creates a
 * PDF of it. Shows how to use Puppeteer to:
 *
 *   1. screenshot a DOM element
 *   2. craft an HTML page on-the-fly
 *   3. produce an image of the element and PDF of the page with the image embedded
 *
 * Usage:
 *   node element-to-pdf.js
 *   USERNAME=ChromiumDev node element-to-pdf.js
 *
 *   --searchable makes "find in page" work:
 *   node element-to-pdf.js --searchable
 *
 * Output:
 *   tweet.png and tweet.pdf
 */

// Include modules that exist in separate files, basically it reads a js file, executes the 
// file and then proceed to return the exports object 
const puppeteer = require('puppeteer');

// process.env is a global variable, injected by node at runtime 
// represent the state of the system environment application 
// it will try to get from process env, if cannot get there, will fallback to default
// here, means fallback to 'ebidel'
const username = process.env.USERNAME || 'ebidel';
const searchable = process.argv.includes('--searchable');

(async() => {

// launch a chromium instance 
const browser = await puppeteer.launch();

// launch a new page 
const page = await browser.newPage();

// set a screen size 
await page.setViewport({width: 1200, height: 800, deviceScaleFactor: 2});
await page.goto(`https://twitter.com/${username}`);

// Can't use elementHandle.click() because it clicks the center of the element
// with the mouse. On tweets like https://twitter.com/ebidel/status/915996563234631680
// there is an embedded card link to another tweet that it clicks.

// find the component, and do some function there
await page.$eval(`.tweet[data-screen-name="${username}"]`, tweet => tweet.click());

// wait for it to be available
await page.waitForSelector('.tweet.permalink-tweet', {visible: true});

// run document.querySelector within the page. If no element matches the selector, return 
// value will be resolved to null
const overlay = await page.$('.tweet.permalink-tweet');
const screenshot = await overlay.screenshot({path: 'tweet.png'});

if (searchable) {
  await page.evaluate(tweet => {
    const width = getComputedStyle(tweet).width;
    tweet = tweet.cloneNode(true);
    tweet.style.width = width;
    document.body.innerHTML = `
      <div style="display:flex;justify-content:center;align-items:center;height:100vh;">;
        ${tweet.outerHTML}
      </div>
    `;
  }, overlay);
} else {
  await page.setContent(`
    <!DOCTYPE html>
    <html>
      <head>
        <style>
          html, body {
            height: 100vh;
            margin: 0;
            display: flex;
            justify-content: center;
            align-items: center;
            background: #fafafa;
          }
          img {
            max-width: 60%;
            box-shadow: 3px 3px 6px #eee;
            border-radius: 6px;
          }
        </style>
      </head>
      <body>
        <img src="data:img/png;base64,${screenshot.toString('base64')}">
      </body>
    </html>
  `);
}

await page.pdf({path: 'tweet.pdf', printBackground: true});

await browser.close();

})();

3.2 crawlsite.js

/**
 * Copyright 2018 Google Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @author ebidel@ (Eric Bidelman)
 */

 /**
  * Discovers all the pages in site or single page app (SPA) and creates
  * a tree of the result in ./output/<site slug/crawl.json. Optionally
  * takes screenshots of each page as it is visited.
  *
  * Usage:
  *   node crawlsite.js
  *   URL=https://yourspa.com node crawlsite.js
  *   URL=https://yourspa.com node crawlsite.js --screenshots
  *
  * Then open the visualizer in a browser:
  *   http://localhost:8080/html/d3tree.html
  *   http://localhost:8080/html/d3tree.html?url=../output/https___yourspa.com/crawl.json
  *
  *Start Server:
  *   node server.js
  *
  */

// provides an API for interacting with the file system 
const fs = require('fs');

// delete files 
const del = require('del');

// nodeJS util module
const util = require('util');

const puppeteer = require('puppeteer');

// high performance Node.js image proccessing, fastest module to resize JPEG, PNG, etc. 
const sharp = require('sharp');

const URL = process.env.URL || 'https://news.polymer-project.org/';
const SCREENSHOTS = process.argv.includes('--screenshots');
const DEPTH = parseInt(process.env.DEPTH) || 2;
const VIEWPORT = SCREENSHOTS ? {width: 1028, height: 800, deviceScaleFactor: 2} : null;
const OUT_DIR = process.env.OUTDIR || `output/${slugify(URL)}`;

const crawledPages = new Map();
const maxDepth = DEPTH; // Subpage depth to crawl site.

function slugify(str) {
  return str.replace(/[\/:]/g, '_');
}

function mkdirSync(dirPath) {
  try {
    dirPath.split('/').reduce((parentPath, dirName) => {
      const currentPath = parentPath + dirName;
      if (!fs.existsSync(currentPath)) {
        fs.mkdirSync(currentPath);
      }
      return currentPath + '/';
    }, '');
  } catch (err) {
    if (err.code !== 'EEXIST') {
      throw err;
    }
  }
}

/**
 * Finds all anchors on the page, inclusive of those within shadow roots.
 * Note: Intended to be run in the context of the page.
 * @param {boolean=} sameOrigin When true, only considers links from the same origin as the app.
 * @return {!Array<string>} List of anchor hrefs.
 */
function collectAllSameOriginAnchorsDeep(sameOrigin = true) {
  const allElements = [];

  const findAllElements = function(nodes) {
    for (let i = 0, el; el = nodes[i]; ++i) {
      allElements.push(el);
      // If the element has a shadow root, dig deeper.
      if (el.shadowRoot) {
        findAllElements(el.shadowRoot.querySelectorAll('*'));
      }
    }
  };

  findAllElements(document.querySelectorAll('*'));

  const filtered = allElements
    .filter(el => el.localName === 'a' && el.href) // element is an anchor with an href.
    .filter(el => el.href !== location.href) // link doesn't point to page's own URL.
    .filter(el => {
      if (sameOrigin) {
        return new URL(location).origin === new URL(el.href).origin;
      }
      return true;
    })
    .map(a => a.href);

  return Array.from(new Set(filtered));
}

/**
 * Crawls a URL by visiting an url, then recursively visiting any child subpages.
 * @param {!Browser} browser
 * @param {{url: string, title: string, img?: string, children: !Array}} page Current page.
 * @param {number=} depth Current subtree depth of crawl.
 */
async function crawl(browser, page, depth = 0) {
  if (depth > maxDepth) {
    return;
  }

  // If we've already crawled the URL, we know its children.
  if (crawledPages.has(page.url)) {
    console.log(`Reusing route: ${page.url}`);
    const item = crawledPages.get(page.url);
    page.title = item.title;
    page.img = item.img;
    page.children = item.children;
    // Fill in the children with details (if they already exist).
    page.children.forEach(c => {
      const item = crawledPages.get(c.url);
      c.title = item ? item.title : '';
      c.img = item ? item.img : null;
    });
    return;
  } else {
    console.log(`Loading: ${page.url}`);

    const newPage = await browser.newPage();
    await newPage.goto(page.url, {waitUntil: 'networkidle2'});

    let anchors = await newPage.evaluate(collectAllSameOriginAnchorsDeep);
    anchors = anchors.filter(a => a !== URL) // link doesn't point to start url of crawl.

    page.title = await newPage.evaluate('document.title');
    page.children = anchors.map(url => ({url}));

    if (SCREENSHOTS) {
      const path = `./${OUT_DIR}/${slugify(page.url)}.png`;
      let imgBuff = await newPage.screenshot({fullPage: false});
      imgBuff = await sharp(imgBuff).resize(null, 150).toBuffer(); // resize image to 150 x auto.
      util.promisify(fs.writeFile)(path, imgBuff); // async
      page.img = `data:img/png;base64,${imgBuff.toString('base64')}`;
    }

    crawledPages.set(page.url, page); // cache it.

    await newPage.close();
  }

  // Crawl subpages.
  for (const childPage of page.children) {
    await crawl(browser, childPage, depth + 1);
  }
}

(async() => {

mkdirSync(OUT_DIR); // create output dir if it doesn't exist.
await del([`${OUT_DIR}/*`]); // cleanup after last run.

const browser = await puppeteer.launch();
const page = await browser.newPage();
if (VIEWPORT) {
  await page.setViewport(VIEWPORT);
}

const root = {url: URL};
await crawl(browser, root);

await util.promisify(fs.writeFile)(`./${OUT_DIR}/crawl.json`, JSON.stringify(root, null, ' '));

await browser.close();

})();

转载请注明来源,欢迎对文章中的引用来源进行考证,欢迎指出任何有错误或不够清晰的表达。可以在下面评论区评论,也可以邮件至 stone2paul@gmail.com

文章标题:Pupperteer Tutorial

文章字数:1.5k

本文作者:Leilei Chen

发布时间:2020-01-30, 23:11:07

最后更新:2020-02-01, 22:06:57

原始链接:https://www.llchen60.com/Pupperteer-Tutorial/

版权声明: "署名-非商用-相同方式共享 4.0" 转载请保留原文链接及作者。

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