Web Scraping Jquery Tutorial

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Simple Screen Scraping using jQuery – Stack Overflow

I have been playing with the idea of using a simple screen-scraper using jQuery and I am wondering if the following is possible.
I have simple HTML page and am making an attempt (if this is possible) to grab the contents of all of the list items from another page, like so:
Main Page:




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Other Page:
//Html

Items to Scrape

  • I want to scrape what is here
  • and what is here
  • and here as well
  • and append it in the main page

So, is it possible using jQuery to pull all of the list item contents from an external page and append them inside of a div?
asked Apr 14 ’11 at 18:31
Rion WilliamsRion Williams70. 8k35 gold badges187 silver badges310 bronze badges
1
Use $ to load the other page into a variable, then create a temporary element and use () to set the contents to the value returned. Loop through the element’s children of nodeType 1 and keep their first children’s nodeValues. If the external page is not on your web server you will need to proxy the file with your own web server.
Something like this:
$({
url: “/”,
dataType: ‘text’,
success: function(data) {
var elements = $(“

“)(data)[0]. getElementsByTagName(“ul”)[0]. getElementsByTagName(“li”);
for(var i = 0; i <; i++) { var theText = elements[i]deValue; // Do something here}}}); answered Apr 14 '11 at 18:53 Ry-♦Ry-203k52 gold badges422 silver badges430 bronze badges 3 Simple scraping with jQuery... // Get HTML from page $( '', function( html) { // Loop through elements you want to scrape content from $(html)("ul")("li")( function(){ var text = $(this)(); // Do something with content})}); answered Jul 3 '17 at 3:17 shrameeshramee3, 69020 silver badges37 bronze badges $("/path/to/other/page", function(data){ $('#data')($('li', data));} answered Apr 14 '11 at 22:25 If this is for the same domain then no problem - the jQuery solution is good. But otherwise you can't access content from an arbitrary website because this is considered a security risk. See same origin policy. There are of course server side workarounds such as a web proxy or CORS headers. Of if you're lucky they will support jsonp. But if you want a client side solution to work with an arbitrary website and web browser then you are out of luck. There is a proposal to relax this policy, but this won't effect current web browsers. answered Apr 15 '11 at 2:24 hojuhoju25. 6k37 gold badges125 silver badges170 bronze badges 4 You may want to consider pjscrape: It allows you to do this from the command-line, using javascript and jQuery. It does this by using PhantomJS, which is a headless webkit browser (it has no window, and it exists only for your script's usage, so you can load complex websites that use AJAX and it will work just as if it were a real browser). The examples are self-explanatory and I believe this works on all platforms (including Windows). answered Sep 27 '13 at 5:22 Camilo MartinCamilo Martin34. 9k20 gold badges106 silver badges151 bronze badges Use YQL or Yahoo pipes to make the cross domain request for the raw page html content. The yahoo pipe or YQL query will spit this back as a JSON that can be processed by jquery to extract and display the required data. On the downside: YQL and Yahoo pipes OBEY the file for the target domain and if the page is to long the Yahoo Pipes regex commands will not run. answered Apr 26 '11 at 2:17 SkizzSkizz6364 silver badges8 bronze badges I am sure you will hit the CORS issue with requests in many cases. From here try to resolve CORS issue. var name = "kk"; var url = " + encodeURIComponent(") + name + "&callback=? "; $(url, function(response) { (response);}); answered Mar 9 '18 at 19:09 KurkulaKurkula6, 89123 gold badges103 silver badges171 bronze badges Not the answer you're looking for? Browse other questions tagged javascript jquery screen-scraping or ask your own question. Client-side web scraping with JavaScript using jQuery and ...

Client-side web scraping with JavaScript using jQuery and …

by CodemzyWhen I was building my first open-source project, codeBadges, I thought it would be easy to get user profile data from all the main code learning websites. I was familiar with API calls and get requests. I thought I could just use jQuery to fetch the data from the various API’s and use name = ‘codemzy’; $(” + name, function(response) { var followers = llowers;});Well, that was easy. But it turns out that not every website has a public API that you can just grab the data you want from. 404: API not foundBut just because there is no public API doesn’t mean you need to give up! You can use web scraping to grab the data, with only a little extra ’s see how we can use client-side web scraping with an example, I will grab my user information from my public freeCodeCamp profile. But you can use these steps on any public HTML first step in scraping the data is to grab the full page html using a jQuery name = “codemzy”;$(” + name, function(response) { (response);});Awesome, the whole page source code just logged to the If you get an error at this stage along the lines of No ‘Access-Control-Allow-Origin’ header is present on the requested resource don’t fret. Scroll down to the Don’t Let CORS Stop You section of this was easy. Using JavaScript and jQuery, the above code requests a page from, like a browser would. And freeCodeCamp responds with the page. Instead of a browser running the code to display the page, we get the HTML that’s what web scraping is, extracting data from, the response is not exactly as neat as the data we get back from an … we have the data, in there we have the source code the information we need is in there, we just have to grab the data we need! We can search through the response to find the elements we ’s say we want to know how many challenges the user has completed, from the user profile response we got the time of writing, a camper’s completed challenges completed are organized in tables on the user profile. So to get the total number of challenges completed, we can count the number of way is to wrap the whole response in a jQuery object, so that we can use jQuery methods like () to get the data. // number of challenges completedvar challenges = $(response)(‘tbody tr’);This works fine — we get the right result. But its is not a good way to get the result we are after. Turning the response into a jQuery object actually loads the whole page, including all the external scripts, fonts and stylesheets from that page…Uh oh! We need a few bits of data. We really don’t need the page the load, and certainly not all the external resources that come with could strip out the script tags and then run the rest of the response through jQuery. To do this, we could use Regex to look for script patterns in the text and remove better still, why not use Regex to find what we are looking for in the first place? // number of challenges completedvar challenges = place(/

[\s|\S]*? <\/thead>/g)(/

/g);And it works! By using the Regex code above, we strip out the table head rows (that did not contain any challenges), and then match all table rows to count the number of challenges ’s even easier if the data you want is just there in the response in plain text. At the time of writing the user points were in the html like

[ 1498]

just waiting to be points = (/

\[ ([\d]*? ) \]<\/h1>/)[1];In the above Regex pattern we match the h1 element we are looking for including the [] that surrounds the points, and group any number inside with ([\d]*? ). We get an array back, the first [0] element is the entire match and the second [1] is our group match (our points) is useful for matching all sorts of patterns in strings, and it is great for searching through our response to get the data we can use the same 3 step process to scrape profile data from a variety of websites:Use client-side JavaScriptUse jQuery to scrape the dataUse Regex to filter the data for the relevant informationUntil I hit a problem, Access DeniedDon’t Let CORS Stop You! CORS or Cross-Origin Resource Sharing, can be a real problem with client-side web security reasons, browsers restrict cross-origin HTTP requests initiated from within scripts. And because we are using client-side Javascript on the front end for web scraping, CORS errors can ’s an example trying to scrape profile data from CodeWars…var name = “codemzy”;$(” + name, function(response) { (response);});At the time of writing, running the above code gives you a CORS related there is noAccess-Control-Allow-Origin header from the place you’re scraping, you can run into bad news is, you need to run these sorts of requests server-side to get around this issue. Whaaaaaaaat, this is supposed to be client-side web scraping?! The good news is, thanks to lots of other wonderful developers that have run into the same issues, you don’t have to touch the back end aying firmly within our front end script, we can use cross-domain tools such as Any Origin, Whatever Origin, All Origins, crossorigin and probably a lot more. I have found that you often need to test a few of these to find the one that will work on the site you are trying to to our CodeWars example, we can send our request via a cross-domain tool to bypass the CORS name = “codemzy”;var url = ” + encodeURIComponent(“) + name + “&callback=? “;$(url, function(response) { (response);});And just like magic, we have our response.
Learn to code for free. freeCodeCamp’s open source curriculum has helped more than 40, 000 people get jobs as developers. Get started
Web Scraping with Javascript and NodeJS - ScrapingBee

Web Scraping with Javascript and NodeJS – ScrapingBee

Javascript has become one of the most popular and widely used languages due to the massive improvements it has seen and the introduction of the runtime known as NodeJS. Whether it’s a web or mobile application, Javascript now has the right tools. This article will explain how the vibrant ecosystem of NodeJS allows you to efficiently scrape the web to meet most of your requirements.
Prerequisites
This post is primarily aimed at developers who have some level of experience with Javascript. However, if you have a firm understanding of Web Scraping but have no experience with Javascript, this post could still prove useful.
Below are the recommended prerequisites for this article:
✅ Experience with Javascript
✅ Experience using DevTools to extract selectors of elements
✅ Some experience with ES6 Javascript (Optional)
⭐ Make sure to check out the resources at the end of this article to learn more!
Outcomes
After reading this post will be able to:
Have a functional understanding of NodeJS
Use multiple HTTP clients to assist in the web scraping process
Use multiple modern and battle-tested libraries to scrape the web
Understanding NodeJS: A brief introduction
Javascript is a simple and modern language that was initially created to add dynamic behavior to websites inside the browser. When a website is loaded, Javascript is run by the browser’s Javascript Engine and converted into a bunch of code that the computer can understand.
For Javascript to interact with your browser, the browser provides a Runtime Environment (document, window, etc. ).
This means that Javascript is not the kind of programming language that can interact with or manipulate the computer or it’s resources directly. Servers, on the other hand, are capable of directly interacting with the computer and its resources, which allows them to read files or store records in a database.
When introducing NodeJS, the crux of the idea was to make Javascript capable of running not only client-side but also server-side. To make this possible, Ryan Dahl, a skilled developer took Google Chrome’s v8 Javascript Engine and embedded it with a C++ program named Node.
So, NodeJS is a runtime environment that allows an application written in Javascript to be run on a server as well.
As opposed to how most languages, including C and C++, deal with concurrency, which is by employing multiple threads, NodeJS makes use of a single main thread and utilizes it to perform tasks in a non-nlocking manner with the help of the Event Loop.
Putting up a simple web server is fairly simple as shown below:
const = require(”);
const PORT = 3000;
const server = eateServer((req, res) => {
atusCode = 200;
tHeader(‘Content-Type’, ‘text/plain’);
(‘Hello World’);});
(port, () => {
(`Server running at PORT:${port}/`);});
If you have NodeJS installed and you run the above code by typing(without the < and >) in node opening up your browser, and navigating to localhost:3000, you will see some text saying, “Hello World”. NodeJS is ideal for applications that are I/O intensive.
HTTP clients: querying the web
HTTP clients are tools capable of sending a request to a server and then receiving a response from it. Almost every tool that will be discussed in this article uses an HTTP client under the hood to query the server of the website that you will attempt to scrape.
Request
Request is one of the most widely used HTTP clients in the Javascript ecosystem. However, currently, the author of the Request library has officially declared that it is deprecated. This does not mean it is unusable. Quite a lot of libraries still use it, and it is every bit worth using.
It is fairly simple to make an HTTP request with Request:
const request = require(‘request’)
request(”, function (
error,
response,
body) {
(‘error:’, error)
(‘body:’, body)})
You can find the Request library at GitHub, and installing it is as simple as running npm install request.
You can also find the deprecation notice and what this means here. If you don’t feel safe about the fact that this library is deprecated, there are other options down below!
Axios
Axios is a promise-based HTTP client that runs both in the browser and NodeJS. If you use TypeScript, then Axios has you covered with built-in types.
Making an HTTP request with Axios is straight-forward. It ships with promise support by default as opposed to utilizing callbacks in Request:
const axios = require(‘axios’)
axios
(”)
((response) => {
(response)})
((error) => {
(error)});
If you fancy the async/await syntax sugar for the promise API, you can do that too. But since top level await is still at stage 3, we will have to make use of an async function instead:
async function getForum() {
try {
const response = await (
”)
(response)} catch (error) {
(error)}}
All you have to do is call getForum! You can find the Axios library at Github and installing Axios is as simple as npm install axios.
SuperAgent
Much like Axios, SuperAgent is another robust HTTP client that has support for promises and the async/await syntax sugar. It has a fairly straightforward API like Axios, but SuperAgent has more dependencies and is less popular.
Regardless, making an HTTP request with Superagent using promises, async/await, or callbacks looks like this:
const superagent = require(“superagent”)
const forumURL = ”
// callbacks
superagent
(forumURL)
((error, response) => {
// promises
(error)})
// promises with async/await
const response = await (forumURL)
You can find the SuperAgent library at GitHub and installing Superagent is as simple as npm install superagent.
For the upcoming few web scraping tools, Axios will be used as the HTTP client.
Note that there are other great HTTP clients for web scrapinglike node-fetch!
Regular expressions: the hard way
The simplest way to get started with web scraping without any dependencies is to use a bunch of regular expressions on the HTML string that you fetch using an HTTP client. But there is a big tradeoff. Regular expressions aren’t as flexible and both professionals and amateurs struggle with writing them correctly.
For complex web scraping, the regular expression can also get out of hand. With that said, let’s give it a go. Say there’s a label with some username in it, and we want the username. This is similar to what you’d have to do if you relied on regular expressions:
const htmlString = ‘
const result = (/

Hello world

‘)
$(”)(‘Hello there! ‘)
$(‘h2’). addClass(‘welcome’)
$()
//

Hello there!

As you can see, using Cheerio is similar to how you’d use jQuery.
However, it does not work the same way that a web browser works, which means it does not:
Render any of the parsed or manipulated DOM elements
Apply CSS or load any external resource
Execute Javascript
So, if the website or web application that you are trying to crawl is Javascript-heavy (for example a Single Page Application), Cheerio is not your best bet. You might have to rely on other options mentionned later in this article.
To demonstrate the power of Cheerio, we will attempt to crawl the r/programming forum in Reddit and, get a list of post names.
First, install Cheerio and axios by running the following command:
npm install cheerio axios.
Then create a new file called, and copy/paste the following code:
const axios = require(‘axios’);
const cheerio = require(‘cheerio’);
const getPostTitles = async () => {
const { data} = await (
”);
const $ = (data);
const postTitles = [];
$(‘div > > a’)((_idx, el) => {
const postTitle = $(el)()
(postTitle)});
return postTitles;} catch (error) {
throw error;}};
getPostTitles()
((postTitles) => (postTitles));
getPostTitles() is an asynchronous function that will crawl the Reddit’s old r/programming forum. First, the HTML of the website is obtained using a simple HTTP GET request with the axios HTTP client library. Then the HTML data is fed into Cheerio using the () function.
With the help of the browser Dev-Tools, you can obtain the selector that is capable of targeting all of the postcards. If you’ve used jQuery, the $(‘div > > a’) is probably familiar. This will get all the posts. Since you only want the title of each post individually, you have to loop through each post. This is done with the help of the each() function.
To extract the text out of each title, you must fetch the DOM element with the help of Cheerio (el refers to the current element). Then, calling text() on each element will give you the text.
Now, you can pop open a terminal and run node You’ll then see an array of about 25 or 26 different post titles (it’ll be quite long). While this is a simple use case, it demonstrates the simple nature of the API provided by Cheerio.
If your use case requires the execution of Javascript and loading of external sources, the following few options will be helpful.
JSDOM: the DOM for Node
JSDOM is a pure Javascript implementation of the Document Object Model to be used in NodeJS. As mentioned previously, the DOM is not available to Node, so JSDOM is the closest you can get. It more or less emulates the browser.
Once a DOM is created, it is possible to interact with the web application or website you want to crawl programmatically, so something like clicking on a button is possible. If you are familiar with manipulating the DOM, using JSDOM will be straightforward.
const { JSDOM} = require(‘jsdom’)
const { document} = new JSDOM(

Hello world

‘)
const heading = document. querySelector(”)
heading. textContent = ‘Hello there! ‘
(‘welcome’)
nerHTML
As you can see, JSDOM creates a DOM. Then you can manipulate this DOM with the same methods and properties you would use while manipulating the browser DOM.
To demonstrate how you could use JSDOM to interact with a website, we will get the first post of the Reddit r/programming forum and upvote it. Then, we will verify if the post has been upvoted.
Start by running the following command to install JSDOM and Axios:
npm install jsdom axios
Then, make a file named and copy/paste the following code:
const { JSDOM} = require(“jsdom”)
const upvoteFirstPost = async () => {
const { data} = await (“);
const dom = new JSDOM(data, {
runScripts: “dangerously”,
resources: “usable”});
const { document} =;
const firstPost = document. querySelector(“div > > “);
();
const isUpvoted = ntains(“upmod”);
const msg = isUpvoted? “Post has been upvoted successfully! “: “The post has not been upvoted! “;
return msg;} catch (error) {
upvoteFirstPost()(msg => (msg));
upvoteFirstPost() is an asynchronous function that will obtain the first post in r/programming and upvote it. To do this, axios sends an HTTP GET request to fetch the HTML of the URL specified. Then a new DOM is created by feeding the HTML that was fetched earlier.
The JSDOM constructor accepts the HTML as the first argument and the options as the second. The two options that have been added perform the following functions:
runScripts: When set to “dangerously”, it allows the execution of event handlers and any Javascript code. If you do not have a clear idea of the credibility of the scripts that your application will run, it is best to set runScripts to “outside-only”, which attaches all of the Javascript specification provided globals to the window object, thus preventing any script from being executed on the inside.
resources: When set to “usable”, it allows the loading of any external script declared using the