This code reads three JavaScript files synchronously from the file system using Node.js's fs module and stores their contents in variables. An HTML string is then created that includes the script elements, which decode and execute the base64-encoded JavaScript code from the three files using eval() and atob().

Cell 9

const fs = require('fs');
const js1 = fs.readFileSync('./sosmethod/dist/www/polyfills.59868df8094f160adda5.js');
const js2 = fs.readFileSync('./sosmethod/dist/www/vendor.59868df8094f160adda5.js');
const js3 = fs.readFileSync('./sosmethod/dist/www/app.59868df8094f160adda5.js');

$html$ = '<bc-app style="position:relative;display:block;min-height:600px;min-width:600px;">hello!</bc-app>'
    + '<script type="application/javascript">eval(atob("' + (new Buffer(js1)).toString('base64') + '"));</script>'
    + '<script type="application/javascript">eval(atob("' + (new Buffer(js2)).toString('base64') + '"));</script>'
    + '<script type="application/javascript">eval(atob("' + (new Buffer(js3)).toString('base64') + '"));</script>';

import * as fs from 'fs';
import * as path from 'path';

// Define constants for file paths
const polyfillsFilePath = './sosmethod/dist/www/polyfills.59868df8094f160adda5.js';
const vendorFilePath = './sosmethod/dist/www/vendor.59868df8094f160adda5.js';
const appFilePath = './sosmethod/dist/www/app.59868df8094f160adda5.js';

// Define a function to read and encode files
function readFileAndEncode(filePath: string): string {
  try {
    const fileBuffer = fs.readFileSync(filePath);
    return fileBuffer.toString('base64');
  } catch (err) {
    console.error(`Error reading file: ${err}`);
    return '';
  }
}

// Read and encode files
const polyfillsContent = readFileAndEncode(polyfillsFilePath);
const vendorContent = readFileAndEncode(vendorFilePath);
const appContent = readFileAndEncode(appFilePath);

// Define the HTML template
const htmlTemplate = `
  
    hello!
    
    
    
  
`;

// Generate the final HTML string
const finalHtml = htmlTemplate
 .replace('%s', polyfillsContent)
 .replace('%s', vendorContent)
 .replace('%s', appContent);

// TODO: Consider using a templating engine for easier maintenance and separation of concerns
// TODO: Add error handling for edge cases (e.g., file not found, invalid file format)

console.log(finalHtml);

Code Breakdown

Importing Modules

const fs = require('fs');

• The fs module is imported, which provides an API for interacting with the file system in Node.js.

Reading Files

const js1 = fs.readFileSync('./sosmethod/dist/www/polyfills.59868df8094f160adda5.js');
const js2 = fs.readFileSync('./sosmethod/dist/www/vendor.59868df8094f160adda5.js');
const js3 = fs.readFileSync('./sosmethod/dist/www/app.59868df8094f160adda5.js');

• Three files are read synchronously from the file system using fs.readFileSync(). The files are stored in the variables js1, js2, and js3.

Creating HTML String

$html$ = '<bc-app style="position:relative;display:block;min-height:600px;min-width:600px;">hello!</bc-app>'
    + '<script type="application/javascript">eval(atob("' + (new Buffer(js1)).toString('base64') + '"));</script>'
    + '<script type="application/javascript">eval(atob("' + (new Buffer(js2)).toString('base64') + '"));</script>'
    + '<script type="application/javascript">eval(atob("' + (new Buffer(js3)).toString('base64') + '"));</script>';

• An HTML string is created and assigned to the variable $html$.
• The string includes a bc-app element with a style attribute and a hello! text node.
• Three script elements are appended to the string, each containing a JavaScript code snippet that:
  1. Decodes a base64-encoded string using atob() and evaluates it using eval().
  2. The decoded string is likely the contents of the three JavaScript files read earlier (js1, js2, and js3).
  3. The decoded JavaScript code is executed in the context of the HTML document.