Generating PDFs from HTML Content using JavaScript

Introduction to Generating PDFs from HTML

In web development, there are scenarios where you might need to generate a PDF document from a specific section of an HTML page. This could be for creating reports, invoices, or any other type of document that needs to be saved or shared in a portable format. JavaScript provides several libraries and techniques to achieve this functionality. In this tutorial, we’ll explore how to use JavaScript to generate PDFs from HTML content.

Understanding the Requirements

Before diving into the implementation details, it’s essential to understand your requirements:

You need to select specific parts of an HTML page (e.g., a div element) and convert its content into a PDF document.
The generated PDF should include styling information if possible.
Optionally, you might want to ignore certain elements within the selected area.

Using jsPDF for Generating PDFs

One popular JavaScript library for generating PDFs is jsPDF. It provides an easy-to-use API for creating PDF documents from scratch or from existing HTML content. Here’s how you can use it:

Including jsPDF and Its Plugins

First, ensure you include the necessary scripts in your project. You’ll need jspdf.js and plugins like jspdf.plugin.from_html.js, jspdf.plugin.split_text_to_size.js, and jspdf.plugin.standard_fonts_metrics.js. These can be downloaded from the jsPDF GitHub repository.

Basic Usage of jsPDF

Here’s a simple example to get you started:

// Create a new jsPDF instance
var doc = new jsPDF();

// Define an element handler for ignoring specific elements by ID
var elementHandler = {
  '#ignoreElement': function (element, renderer) {
    return true;
  }
};

// Get the source HTML content
var source = window.document.getElementsByTagName("body")[0];

// Generate the PDF from the HTML content with specified options
doc.fromHTML(
  source,
  15,
  15,
  {
    'width': 180,
    'elementHandlers': elementHandler
  }
);

// Output the generated PDF as a data URL in a new window
doc.output("dataurlnewwindow");

Limitations of jsPDF

While jsPDF is powerful, it has some limitations:

It supports special element handlers only for IDs (not classes or other selectors).
Styling information might not be perfectly preserved, as it primarily relies on the browser’s rendering engine to interpret CSS styles.
Certain elements like textarea and input values are not directly supported.

Alternative Approaches

For scenarios where jsPDF is not ideal, consider alternative approaches:

Using Window Print Functionality

You can create a new window with the content you want to print and then invoke the browser’s print functionality. This method allows users to select "Save as PDF" from their printer options.

function printDiv(divId) {
  let mywindow = window.open('', 'PRINT', 'height=650,width=900,top=100,left=150');

  mywindow.document.write('<html><head><title>Printable Content</title></head><body >');
  mywindow.document.write(document.getElementById(divId).innerHTML);
  mywindow.document.write('</body></html>');

  mywindow.document.close(); // Necessary for IE >= 10
  mywindow.focus(); // Necessary for IE >= 10

  mywindow.print();
  mywindow.close();

  return true;
}

Server-Side Generation with Puppeteer

For more control over the PDF generation process, consider using a server-side solution like Puppeteer. It allows you to launch a headless Chrome browser instance, navigate to your content, and save it as a PDF.

const puppeteer = require('puppeteer');

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.goto('https://your-domain.com/path-to-content', {
    waitUntil: 'networkidle2',
  });
  await page.pdf({ path: 'content-file-path.pdf', format: 'a4' });

  await browser.close();
})();

Conclusion

Generating PDFs from HTML content using JavaScript can be achieved through various libraries and techniques, each with its strengths and limitations. jsPDF offers a straightforward way to convert HTML into PDFs but has limitations regarding styling and element support. Alternative approaches like leveraging the browser’s print functionality or using server-side tools like Puppeteer provide more flexibility and control over the output. The choice of method depends on your specific requirements and the complexity of the content you’re working with.