Cookbooks
Google Apps Script
Chapter 11. HTML and the Web
Downloading a web page

Google Apps Script:
Downloading a web page

How to:

In Google Apps Script, the UrlFetchApp service is pivotal for downloading web content. Below is a step-by-step guide and a simple example demonstrating how to fetch and log the HTML content of a webpage:

  1. Basic Fetch Operation:
function downloadWebPage() {
  var url = "http://example.com";
  var response = UrlFetchApp.fetch(url);
  var content = response.getContentText();
  Logger.log(content);
}
  • This code fetches the HTML content of example.com and logs it. It’s a straightforward demonstration of getting a web page’s source without any additional parameters.
  1. Handling Redirects and HTTPS:

For HTTPS or handling redirects, the code remains largely the same, but consider implementing error handling or specific options for redirects:

function downloadSecureWebPage() {
  var options = {
    'followRedirects': true, // Automatically follow redirects
    'muteHttpExceptions': true // Mute possible exceptions to handle them gracefully
  };
  
  var url = "https://example.com";
  var response = UrlFetchApp.fetch(url, options);
  Logger.log(response.getContentText());
}
  1. Rate Limits and Quotas:

Be mindful of Google Apps Script’s quotas; heavy usage may require error handling for rate limits.

Deep Dive

Historically, web content download and manipulation began with simple HTTP requests, evolving significantly with the advent of scripting languages. Google Apps Script allows straightforward execution of such tasks within the G Suite ecosystem, leveraging Google’s robust infrastructure. The UrlFetchApp service is a core element of this functionality, encapsulating complex HTTP/S requests into a simpler application-level interface.

Despite its convenience, Google Apps Script may not always be the best tool for heavy-duty web scraping or when complex post-processing of fetched data is required due to execution time limits and quotas imposed by Google. In such cases, dedicated web scraping frameworks or languages designed for asynchronous I/O operations, such as Node.js with libraries like Puppeteer or Cheerio, might offer more flexibility and power.

Furthermore, while Google Apps Script is an excellent tool for integrating with Google Services (like Sheets, Docs, and Drive) and performing lightweight data fetch operations, it’s crucial to keep in mind its execution environment’s limitations. For intensive tasks, consider using Google Cloud Functions or Apps Script’s advanced services with external compute resources for processing.

Parsing HTML