刮取Javascript呈现的网页，该网页引用R中的外部JavaScript脚本

Question

I am trying to scrape this webpage: https://www.mustardbet.com/sports/events/302698

Since the webpage seems to be rendered dynamically, I am following this tutorial: https://www.datacamp.com/community/tutorials/scraping-javascript-generated-data-with-r#gs.dZEqev8

As the tutorial suggests, I save a file named "scrape_mustard.js" with the following code:

// scrape_mustard.js

var webPage = require('webpage');
var page = webPage.create();

var fs = require('fs');
var path = 'mustard.html'

page.open('https://www.mustardbet.com/sports/events/302698', function (status) {
  var content = page.content;
  fs.write(path,content,'w')
  phantom.exit();
});

Then, I perform

system("./phantomjs scrape_mustard.js")

but I get the error:

ReferenceError: Can't find variable: Set

  https://www.mustardbet.com/assets/js/index.dfd873fb.js:1
  https://www.mustardbet.com/assets/js/index.dfd873fb.js:1 in t
  https://www.mustardbet.com/assets/js/index.dfd873fb.js:1
  https://www.mustardbet.com/assets/js/index.dfd873fb.js:1 in t
  https://www.mustardbet.com/assets/js/index.dfd873fb.js:1
  https://www.mustardbet.com/assets/js/index.dfd873fb.js:1 in t
  https://www.mustardbet.com/assets/js/index.dfd873fb.js:1
  https://www.mustardbet.com/assets/js/index.dfd873fb.js:1 in t
  https://www.mustardbet.com/assets/js/index.dfd873fb.js:1

Now, when I paste " https://www.mustardbet.com/assets/js/index.dfd873fb.js " into my browser I can see that it's javascript, and that I probably need to either (1) save that as a file, or (2) include it in scrape_mustard.js.

But if (1), I don't know how to then reference that new file, and if (2), I don't know how to define all that javascript properly so that it can be used.

I'm a complete newbie to javascript, but maybe this problem is not too difficult?

Thanks for your help!

Answer 1

I was able to scrape using the js module puppeteer.js .

Download node.js here . node.js comes with npm which makes your life easier when comes to install modules. You need to install puppeteer using npm .

In RStudio, make sure you are on your working directory when you are installing puppeteer.js . Once node.js is installed, do ( source ):

system("npm i puppeteer")

scrape_mustard.js :

// load modules
const fs = require("fs");
const puppeteer = require("puppeteer");

// page url
url = "https://www.mustardbet.com/sports/events/302698";

scrape = async() => {
    const browser = await puppeteer.launch({headless: false}); // open browser
    const page = await browser.newPage(); // open new page
    await page.goto(url, {waitUntil: "networkidle2", timeout: 0}); // go to page
    await page.waitFor(5000); // give it time to load all the javascript rendered content
    const html = await page.content(); // copy page contents
    browser.close(); // close chromium
    return html // return html object
};

scrape().then((value) => {
    fs.writeFileSync("./stackoverflow/page.html", value) // write the object being returned by scrape()
});

To run scrape_mustard.js in R :

library(magrittr)

system("node ./stackoverflow/scrape_mustard.js")

html <- xml2::read_html("./stackoverflow/page.html")

oddsMajor <- html %>% 
  rvest::html_nodes(".odds-major")

betNames <- html %>% 
  rvest::html_nodes("h3")

Console output:

{xml_nodeset (60)}
 [1] <span class="odds-major">2</span>
 [2] <span class="odds-major">14</span>
 [3] <span class="odds-major">15</span>
 [4] <span class="odds-major">16</span>
 [5] <span class="odds-major">17</span>
 [6] <span class="odds-major">23</span>
 [7] <span class="odds-major">25</span>
 [8] <span class="odds-major">32</span>
 [9] <span class="odds-major">33</span>
[10] <span class="odds-major">39</span>
[11] <span class="odds-major">47</span>
[12] <span class="odds-major">54</span>
[13] <span class="odds-major">55</span>
[14] <span class="odds-major">58</span>
[15] <span class="odds-major">58</span>
[16] <span class="odds-major">64</span>
[17] <span class="odds-major">73</span>
[18] <span class="odds-major">73</span>
[19] <span class="odds-major">92</span>
[20] <span class="odds-major">98</span>
...
> betNames
{xml_nodeset (60)}
 [1] <h3>Charles Howell III</h3>\n
 [2] <h3>Brian Harman</h3>\n
 [3] <h3>Austin Cook</h3>\n
 [4] <h3>J.J. Spaun</h3>\n
 [5] <h3>Webb Simpson</h3>\n
 [6] <h3>Cameron Champ</h3>\n
 [7] <h3>Peter Uihlein</h3>\n
 [8] <h3>Seung-Jae Im</h3>\n
 [9] <h3>Nick Watney</h3>\n
[10] <h3>Graeme McDowell</h3>\n
[11] <h3>Zach Johnson</h3>\n
[12] <h3>Lucas Glover</h3>\n
[13] <h3>Corey Conners</h3>\n
[14] <h3>Luke List</h3>\n
[15] <h3>David Hearn</h3>\n
[16] <h3>Adam Schenk</h3>\n
[17] <h3>Kevin Kisner</h3>\n
[18] <h3>Brian Gay</h3>\n
[19] <h3>Patton Kizzire</h3>\n
[20] <h3>Brice Garnett</h3>\n
...

I am sure it can be done with phantomjs but I've found puppeteer easier to scrape javascript-rendered webpages. Also keep in mind that phantomjs is no longer being developed .