webworker.js

// ***************************    Main.js    **********************************
var worker = new Worker('/Scripts/fileupload.js'); // fileupload.js is our webworker script file

worker.onmessage = (e) => { // called when ww calls self.postMessage
    console.log(e.data);
};

worker.onerror = (e) => { // onerror
   console.log('ERROR: Line ', e.lineno, ' in ', e.filename, ': ', e.message);
}

worker.postMessage({ 'files': files }); // calls self.onmessagein the ww
worker.terminate(); // called to terminate the ww

// ***************************    fileupload.js (WebWorker)   **********************************

self.onmessage = (e) => { // ww receives message
    for (var j = 0; j < e.data.files.length; j++)
        files.push(e.data.files[j]);
    if (p) {
        process();
    }
};

// calls worker.onmessage
// ww posts message back to page or script which created the ww
self.postMessage(blob.name + " Uploaded Succesfully");