I am working on a Chrome Extension which is structured like this :
the service_worker : fetches a list of compatible websites every day and if it is compatible, I will inject a 'widget' in the website
the widget : is a React App injected inside the page (a 300x300px position:absolute div) that can help the user and that is linked to the user account from my website, for example he can save a product from Amazon and see it later in his account in my website.
My problem is the communication between these two parts.
An example :
I want to check if the user has currently a session opened in my website, if yes, in the React App (the widget) I will render him some tools and his items, and if not I will render him a link to login in my website.
Tried solutions:
Call my website API directly from the widget : but I dont want to make the verification from the widget because it is a part of the webpage and I am afraid of a cookie/token hijacking (tell me if i'm wrong).
Using CustomEvents to get a response : I found this useful post, the problem is that as said in the 5th point I cant really wait for a response from the service_worker and store it.
Using CustomEvents with callbacks : I also can't send a callback function as said here.
Using sendMessage from Chrome API : To use this between webpage and the service_worker you need to specify in the manifest.json the pattern of every website that needs to use it, but the list can change every day. Also the domain cannot be *, and we cannot use <all_urls>
So, my communication is only working from the web page to the extension but not in the opposite way.
Can you advise me a way of making this work ?
Thanks !
I am trying to import data from the following website to Google Sheets. I want to import all the matches for the day.
https://www.tournamentsoftware.com/tournament/b731fdcd-a0c8-4558-9344-2a14c267ee8b/Matches
I have tried importxml and importhtml, but it seems this does not work as the website uses JavaScript. I have also tried to use Apipheny without any success.
When using Apipheny, the error message is
'Failed to fetch data - please verify your API Request: {DNS error'
Tl;Dr
Adapted from my answer to How to know if Google Sheets IMPORTDATA, IMPORTFEED, IMPORTHTML or IMPORTXML functions are able to get data from a resource hosted on a website? (also posted by me)
Please spend some time learning how to use the browsers developers tools so you will be able to identify
if the data is already included in source code of the webpage as JSON / literal JavaScript object or in another form
if the webpage is doing a GET or POST requests to retrieve the data and when those requests are done (i.e. as some point of the page parsing, or on event)
if the requests require data from cookies
Brief guide about how to use the web browser to find useful details about the webpage / data to import
Open the source code and look if the required data is included. Sometimes the data is included as JSON and added to the DOM using JavaScript. In this case it might be possible to retrieve the data by using the Google Sheets functions or URL Fetch Service from Google Apps Script.
Let say that you use Chrome. Open the Dev Tools, then look at the Elements tab. There you will see the DOM. It might be helpful to identify if the data that you want to import besides being on visible elements is included in hidden / not visible elements like <script> tags.
Look at Source, there you might be able to see the JavaScript code. It might include the data that you want to import as JavaScript object (commonly referred as JSON).
There are a lot of questions about google-sheets +web-scraping that mentions problems using importhtml and/or importxml that already have answers and even many include code (JavaScript snippets, Google Apps Script functions, etc.) that might save you to have to use an specialized web-scraping tool that has a more stepped learning curve. At the bottom of this answer there is a list of questions about using Google Sheets built-in functions, including annotations of the workaround proposed.
On Is there a way to get a single response from a text/event-stream without using event listeners? ask about using EventSource. While this can't be used on server side code, the answer show how to use the HtmlService to use it on client-side code and retrieve the result to Google Sheets.
As you already realized, the Google Sheets built-in functions importhtml(), importxml(), importdata() and importfeed() only work with static pages that do not require signing in or other forms of authentication.
When the content of a public page is created dynamically by using JavaScript, it cannot be accessed with those functions, by the other hand the website's webmaster may also purposefully have prevented web scraping.
How to identify if content is added dynamically
To check if the content is added dynamically, using Chrome,
Open the URL of the source data.
Press F12 to open Chrome Developer Tools
Press Control+Shift+P to open the Command Menu.
Start typing javascript, select Disable JavaScript, and then press Enter to run the command. JavaScript is now disabled.
JavaScript will remain disabled in this tab so long as you have DevTools open.
Reload the page to see if the content that you want to import is shown, if it's shown it could be imported by using Google Sheets built-in functions, otherwise it's not possible but might be possible by using other means for doing web scraping.
According to Wikipedia,
Web scraping, web harvesting, or web data extraction is data scraping used for extracting data from websites.
Use of robots.txt to block Web crawlers
The webmasters could use robots.txt file to block access to website. In such case the result will be #N/A Could not fetch URL.
Use of User agent
The webpage could be designed to return a special a custom message instead of the data.
Below there are more details about how Google Sheets built-in "web-scraping" functions works
IMPORTDATA, IMPORTFEED, IMPORTHTML and IMPORTXML are able to get content from resources hosted on websites that are:
Publicly available. This means that the resource doesn't require authorization / to be logged in into any service to access it.
The content is "static". This mean that if you open the resource using the view source code option of modern web browsers it will be displayed as plain text.
NOTE: The Chrome's Inspect tool shows the parsed DOM; in other works the actual structure/content of the web page which could be dynamically modified by JavaScript code or browser extensions/plugins.
The content has the appropriated structure.
IMPORTDATA works with structured content as csv or tsv doesn't matter of the file extension of the resource.
IMPORTFEED works with marked up content as ATOM/RSS
IMPORTHTML works with marked up content as HTML that includes properly markedup list or tables.
IMPORTXML works with marked up content as XML or any of its variants like XHTML.
The content doesn't exceeds the maximum size. Google haven't disclosed this limit but the below error will be shown when the content exceeds the maximum size:
Resource at url contents exceeded maximum size.
Google servers are not blocked by means of robots.txt or the user agent.
On W3C Markup Validator there are several tools to checkout is the resources had been properly marked up.
Regarding CSV check out Are there known services to validate CSV files
It's worth to note that the spreadsheet
should have enough room for the imported content; Google Sheets has a 10 million cell limit by spreadsheet, according to this post a columns limit of 18278, and a 50 thousand characters as cell content even as a value or formula.
it doesn't handle well large in-cell content; the "limit" depends on the user screen size and resolution as now it's possible to zoom in/out.
References
https://developers.google.com/web/tools/chrome-devtools/javascript/disable
https://en.wikipedia.org/wiki/Web_scraping
Related
Using Google Apps Script to scrape Dynamic Web Pages
Scraping data from website using vba
Block Website Scraping by Google Docs
Is there a way to get a single response from a text/event-stream without using event listeners?
Software Recommendations
Web scraping tool/software available for free?
Recommendations for web scraping tools that require minimal installation
Web Applications
The following question is about a different result, #N/A Could not fetch URL
Inability to use IMPORTHTML in Google sheets
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One of the answers includes Google Apps Script code to get data from a JSON source. As of January 4th 2023, it's not longer working, very likely because Yahoo! Finance is now encrying the JSON. See the Tainake's answer to How to pull Yahoo Finance Historical Price Data from its Object with Google Apps Script? for script using Crypto.js to handle this.
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ImportXML is good for basic tasks, but it won't get you too far if you are serious in scraping:
The approach only works with the most basic websites (no SPAs rendered in browsers can be scraped this way. Any basic web scraping protection or connectivity issue breaks the process, and there isn't any control over HTTP request geo location, or number of retries) - and Yahoo Finance is not a simple website
If the target website data requires some cleanup post-processing, it's getting very complicated since you are now "programming with Excel formulas", rather a painful process compared to regular code writing in conventional programming languages
There isn't any proper launch and cache control, so the function can be triggered occasionally and if the HTTP request fails, cells will be populated with ERR! values
I recommend using proper tools (automation framework and scraping engine which can render JavaScript-powered websites) and use Google Sheets just for basic storage purposes:
https://youtu.be/uBC752CWTew (Pipedream for automation and ScrapeNinja engine for scraping)
I'm having a Google spreadsheet embedded in an (Episerver) page and the spreadsheet is editable. I also have a trigger onEdit in the sheet. When running that script 'onEdit' I'd like to get the info from current page using "document.getElementsByClassName().innerHTML" to get the context of the current situation, meaning fetching the username that is currently logged in that is displayed in the section within an element.
I'm getting the error 'document is not defined' and I got the reason. This is working just running the script as a pure javascript on the site. There is no success using GAS URLFetchApp since it not fetching the current page with the current user logged in. As I see it I have two possible options:
a) Is there anyway to use HTML DOM (document...) within Google Apps Script?
b) Can I fetch current page instead of fetching a new URL in Google Apps Script?
A) I think your only option here is to us the XML service.
B) I don't believe so, as the script is self contained, and doesn't have the ability to interact with the browser. You need to know a URL in order to fetch it.
However, you mention that part of what you'd like to do is fetch the user that is currently logged in, so perhaps you might be interested in the '.getActiveUser()' method? It might be a potential solution.
I'm currently working on a google chrome extension which needs to use notifications.
It's meant to extract an image from a site (got that part), upload it to imgur and then use it as the icon for the notification. My problem is:
All icons have to be listed under 'web_accessible_resources' before being used in a notification. However, my problem is that I create the icon while the extension is already running and I therefore cannot add it to the manifest.
Is there any workaround for this?
Try a data URI. This is extra text to reach the 30-character minimum.
I’m writing a Chrome extension for Gmail. I want to replace the default list view with a custom made one.
I want to fetch all message bodies for all displayed messages. How can I do so from within a Chrome extension?
Gmail has ATOM feed of unread messages. It doesn’t have a feed for all messages.
Gmail has a gmonkey object. 1.0 version is documented. There is also undocumented 2.0 version. None of them allow me to fetch a message body.
Gmail for iPad stores all messages in WebSQL storage. Unfortunately, desktop Gmail does not.
If you don't get any other answers, you can always do it the hard way, via Content Scripts, basically by injecting jQuery, scraping message bodies, readjusting DOM structures, etc.