I’m currently creating my google chrome extension that inject a button in netsuite and when this button is clicked it should trigger the native Excel export Netsuite button and everything is working but I want to use SheetJs to convert directly the XLS file into XLSX.

I tried a lot of different approach but the XLS file keeps getting downloaded and the conversion is not working and this is my background script code:

importScripts ["xlsx.full.min.js"];

console.log('Background script loading...');

chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  console.log('Message received in background:', message);
  if (message.action === "exportStarted") {
    console.log('Export process started by user');
    sendResponse({status: 'received', message: 'Export start acknowledged'});
    watchForDownload();
  }
  return true;  // Keeps the message channel open for asynchronous response
});

function watchForDownload() {
  console.log('Watching for download...');
  let attempts = 0;
  const maxAttempts = 10;
  
  function checkDownloads() {
    chrome.downloads.search({limit: 1, orderBy: ['-startTime']}, (downloads) => {
      console.log('Recent downloads:', downloads);
      if (downloads && downloads.length > 0) {
        const download = downloads[0];
        console.log('Most recent download:', download);
        if (download.filename.toLowerCase().endsWith('.xls')) {
          console.log('XLS file detected, attempting conversion');
          convertToXLSX(download);
        } else {
          console.log('Not an XLS file, continuing to watch...');
          retryCheck();
        }
      } else {
        console.log('No downloads found, continuing to watch...');
        retryCheck();
      }
    });
  }

  function retryCheck() {
    attempts++;
    if (attempts < maxAttempts) {
      console.log(`Retry attempt ${attempts} of ${maxAttempts}`);
      setTimeout(checkDownloads, 1000);  // Check every second
    } else {
      console.log('Max attempts reached, stopping watch');
    }
  }

  checkDownloads();
}

function convertToXLSX(downloadItem) {
  console.log('Starting conversion for:', downloadItem.filename);
  fetch(downloadItem.url)
    .then(response => response.arrayBuffer())
    .then(data => {
      console.log('XLS data fetched, size:', data.byteLength);
      const workbook = XLSX.read(new Uint8Array(data), {type: 'array'});
      console.log('Workbook read, sheets:', workbook.SheetNames);
      const xlsxOutput = XLSX.write(workbook, {bookType: 'xlsx', type: 'array'});
      console.log('XLSX data created, size:', xlsxOutput.length);
      
      const blob = new Blob([xlsxOutput], {type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'});
      const url = URL.createObjectURL(blob);
      
      const newFilename = downloadItem.filename.replace(/.xls$/i, '.xlsx');
      console.log('New filename:', newFilename);
      
      chrome.downloads.download({
        url: url,
        filename: newFilename,
        saveAs: false
      }, (downloadId) => {
        console.log('XLSX download started, id:', downloadId);
        URL.revokeObjectURL(url);
        chrome.downloads.removeFile(downloadItem.id, () => {
          console.log('Original XLS file removed');
        });
      });
    })
    .catch(error => console.error('Conversion error:', error));
}

console.log('Background script loaded and running.');