Use nodejs to convert html to pdf

With the continuous development of Internet technology, more and more applications need to convert web content to PDF format to make it easier to share and download. In this process, Node.js can be used as a powerful tool to convert HTML documents to PDF format. This article will cover the process of converting HTML to PDF using Node.js.

1. Install necessary dependencies

Before you begin, you need to install the following necessary packages in your system:

• Node. js development environment
• npm - Node.js package manager
• wkhtmltopdf - A tool to generate PDF from web pages

Wkhtmltopdf is a command based on the WebKit engine It is an online tool that can convert html documents into pdf files. It also supports adding watermarks, headers and footers and many other features.

Under Ubuntu system, you can install wkhtmltopdf through the following command:

sudo apt-get install wkhtmltopdf

2. Install dependencies

Next, you need to install pdfkit and fs module, both of which can be installed through the npm package manager.

Enter the following command on the command line to install:

npm install pdfkit

npm install fs

3. Writing code

After installing the relevant dependencies, you can start writing JavaScript code . You can create a file named "html-to-pdf.js" and write the following code:

const pdfkit = require('pdfkit');
const fs = require('fs');
const wkhtmltopdf = require('wkhtmltopdf');

// 生成 PDF
function generatePDF(html, options, callback) {
    // 创建文件流
    const inputStream = fs.createReadStream(html);

    // 调用 wkhtmltopdf
    wkhtmltopdf(inputStream, options, (error, stream) => {
        if (error) {
            callback(error);
        } else {
            callback(null, stream);
        }
    });
}

// 写 PDF
function writePDF(doc, path, callback) {
    const writeStream = fs.createWriteStream(path);

    writeStream.on('error', (error) => {
        callback(error);
    });

    doc.pipe(writeStream);

    doc.end();
}

// 创建 PDF
function createPDF(html, path, options, callback) {
    const doc = new pdfkit();

    generatePDF(html, options, (error, stream) => {
        if (error) {
            callback(error);
        } else {
            doc.on('pageAdded', () => {
                doc.image(stream, {
                    fit: [doc.page.width - 100, doc.page.height - 100],
                    align: 'center',
                    valign: 'center'
                });
            });

            doc.pipe(fs.createWriteStream(path));

            doc.end();

            callback(null, path);
        }
    });
}

// 导出模块
module.exports = {
    createPDF,
    writePDF,
    generatePDF
};

In this code, we introduced the pdfkit, fs and wkhtmltopdf modules and wrote three Functions: generatePDF, writePDF and createPDF.

The generatePDF function is used to convert HTML files to PDF format. It requires passing three parameters: html, options and callback.

The writePDF function is used to write PDF documents to the file system. It requires passing three parameters: doc, path and callback.

The createPDF function is the control center of the entire process. It can call the generatePDF and writePDF functions to complete the process of converting HTML to PDF.

4. Convert HTML to PDF using Node.js

Now that you have finished writing the code, you can start converting HTML to PDF using Node.js. You can enter the following command in the command line:

node html-to-pdf.js

Or, you can also use this module in your own project:

const htmlToPdf = require('./html-to-pdf');

htmlToPdf.createPDF('test.html', 'test.pdf', {
   pageSize: 'letter',
   marginTop: '0mm',
   marginBottom: '0mm',
   marginLeft: '0mm',
   marginRight: '0mm'
}, (err, result) => {
   if (err) {
      console.error(err);
      return;
   }
   console.log('File saved to: ' + result);
});

In this example, we use the createPDF function to test .html is converted to test.pdf with page size and margins set.

5. Summary

In this article, we introduced how to use Node.js to convert HTML to PDF. The specific steps include installing dependencies, writing code, and using Node.js for conversion and more. If you need to handle extensive HTML conversion tasks, using Node.js can provide you with an efficient, flexible, and scalable solution.

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