Uses the Puppeteer node module to extract the coverage JS from Chrome, for a specific URL.

coverageJS.js

const puppeteer = require('puppeteer');

// Include to be able to export files with node
const fs = require('fs');

// This prepares the filenames for the coverage .js files 
function exportJSFileName(url) {
    
    // Remove https:// from the beginning of the string
    // Remove .js* from the end of the string
    var newFileName = url.substring(8, url.search("\\.js"));
    
    // Replace all forward slashes with hyphens
    newFileName = newFileName.replace(/\//g, "-");
    
    // Return filename with .js concatenated at the end    
    return newFileName+".js";
}

(async () => {
    const browser = await puppeteer.launch();
    const page = await browser.newPage();
    
    // Enable JavaScript coverage
    await Promise.all([
      page.coverage.startJSCoverage()
    ]);
    
    // Extract coverage JS from this URL
    await page.goto('https://google.com');
    
    // Disable JavaScript coverage
    const jsCoverage = await Promise.all([
      page.coverage.stopJSCoverage()
    ]);
    
    // Investigate JS Coverage and Extract Used JS
    const coverage = [...jsCoverage];
    
    for (const entry of coverage[0]) {
        
        // Init covered_js
        let covered_js = "// Generated by Superfein JS Coverage Tool \n" + 
                         "// ************************************ \n\n";
    
        // Check if the js asset contains '.js' in the URL, if it does then export the coverage JS
        // Ignoring inline scripts in the web page
        if ( entry.url.search("\\.js") !== -1 ) {
        
            for (const range of entry.ranges) {
                
                // Iterate through the .json ranges
                covered_js += entry.text.slice(range.start, range.end) + "\n";
            }
            
            // Create and export each coverage JS file
            fs.writeFile("./js_assets/"+exportJSFileName(entry.url), covered_js, function(err) {
                if(err) {
                    return console.log(err);
                }
                console.log("The file "+exportJSFileName(entry.url)+" was saved!");
            });
        }
    }
    
    await browser.close();
})();