Web Scraping in a Google Chrome Extension (JavaScript + Chrome APIs)

Question

What are the best options for performing Web Scraping of a not currently open tab from within a Google Chrome Extension with JavaScript and whatever more technologies are available. Other JavaScript-libraries are also accepted.

The important thing is to mask the scraping to behave like a normal web-request. No indications of AJAX or XMLHttpRequest, like X-Requested-With: XMLHttpRequest or Origin.

The scraped content must be accessible from JavaScript for further manipulation and presentation within the extension, most probably as a string.

Are there any hooks in any WebKit/Chrome-specific API:s that can be used to make a normal web-request and get the results for manipulation?

var pageContent = getPageContent(url); // TODO: Implement
var items = $(pageContent).find('.item');
// Display items with further selections

Bonus-points to make this work from a local file on disk, for initial debugging. But if that is the only point is stopping a solution, then disregard the bonus-points.

Solution 1

Attempt to use XHR2 responseType = "document" and fall back on (new DOMParser).parseFromString(responseText, getResponseHeader("Content-Type")) with my text/html patch. See https://gist.github.com/1138724 for an example of how I detect responseType = "document support (synchronously checking response === null on an object URL created from a text/html blob).

Use the Chrome WebRequest API to hide X-Requested-With, etc. headers.

Solution 2

A lot of tools have been released since this question was asked.

artoo.js is one of them. It's a piece of JavaScript code meant to be run in your browser's console to provide you with some scraping utilities. It can also be used as a chrome extension.

Solution 3

If you are fine looking at something beyond a Google Chrome Plugin, look at phantomjs which uses Qt-Webkit in background and runs just like a browser incuding making ajax requests. You can call it a headless browser as it doesn't display the output on a screen and can quitely work in background while you are doing other stuff. If you want, you can export out images, pdf out of the pages it fetches. It provides JS interface to load pages, clicking on buttons etc much like you have in a browser. You can also inject custom JS for example jQuery on any of the pages you want to scrape and use it to access the dom and export out desired data. As its using Webkit its rendering behaviour is exactly like Google Chrome.

Another option would be to use Aptana Jaxer which is based on Mozilla Engine and is very good concept in itself. It can be used as a simple scraping tool as well.

Solution 4

Web scraping is kind of convoluted in a Chrome Extension. Some points:

• You run content scripts for access to the DOM.
• Background pages (one per browser) can send and receive messages to content scripts. That is, you can run a content script that sets up an RPC endpoint and fires a specified callback in the context of the background page as a response.
• You can execute content scripts in all frames of a webpage, then stitch the document tree (composed of the 1..N frames that the page contains) together.
• As S.K. suggested, your background page can send the data as an XMLHttpRequest to some kind of lightweight HTTP server that listens locally.

Solution 5

I'm not sure it's entirely possible with just JavaScript, but if you can set up a dedicated PHP script for your extension that uses cURL to fetch the HTML for a page, the PHP script could scrape the page for you and your extension could read it in through an AJAX request.

The actual page being scraped wouldn't know it's an AJAX request, however, because it is being accessed through cURL.

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Comments

[Seb Nilsson]

I've tried that, but I can't access the content of the Iframe, as specified in the W3C-standards. Was hoping Chrome Extensions would give me something around that.

[Seb Nilsson]

Could you format your response a bit and maybe provide a couple of lines of code for an example, please.

[Seb Nilsson]

Really got me going there for a while, but none of them seem to be able to integrate into a Google Chrome Extension unfortunately :( They are both stand-alone products that has to be handled in its own environment. Very nice try though.

[Anshul]

@SebNilsson Forgot to mention that earlier, have edited the answer. I assumed your need to have the solution as chrome extension is solely based on your need to get a real browser interacting with the site.

[Seb Nilsson]

Jeez, calm down. It was just formatted like a 5-year-old, so I thought you could clean up your "fastest gun in the west"-answer.

[Seb Nilsson]

And no, sorry, it doesn't work. Still getting the same old "origin null"-error.

[hamczu]

You can access iframe content by including content script. This is best solution I have found and I'm using it in many of my extensions.

[denysonique]

By launching chrome with $ chrome --disable-web-security you can access iframes, but some sites dont like this and breakout of iframes

[MGOwen]

This is for scraping pages that are currently open in a chrome tab, correct?