For security reasons, we cannot fire the select file dialog without a user action.
Hence the buttons to load local MOCs.
Perform all others actions (load from url/create/manipulate/save) from the console. MOCs from local FITS: Load FITS
S-MOCs from local FITS/JSON/ASCII: Load S-MOC
T-MOCs from local FITS/JSON/ASCII: Load T-MOC
ST-MOCs from local FITS/JSON/ASCII: Load ST-MOC
MOC from local multi-order-map (FITS): Load MultiOrderMap

Try copy/paste and exec the following lines of javascript from your web-browser console:

(async () => {      
  // Load 2MASS and SDSS DR12 MOCs from CDS      
  await moc.fromFitsUrl('2mass', 'http://alasky.u-strasbg.fr/footprints/tables/vizier/II_246_out/MOC');
  await moc.fromFitsUrl('sdss12', 'http://alasky.u-strasbg.fr/footprints/tables/vizier/V_147_sdss12/MOC');
  
  // List MOCs loaded in the page
  console.log(moc.list());
        
  // Init a timer
  console.time('timer');
  // Performs MOC intersection
  moc.and('2mass', 'sdss12', '2mass_inter_sdss12');
  // Log time
  console.timeLog('timer', 'Intersection');
  // Performs MOC union
  moc.or('2mass', 'sdss12', '2mass_union_sdss12');
  // Log time
  console.timeLog('timer', 'Union');
  // Degrade to order 2 the result of the intersection      
  moc.degrade('2mass_inter_sdss12', 2, '2mass_inter_sdss12_d2')
  // Remove timer
  console.timeEnd('timer');
        
  // List MOCs loaded in the page
  console.log(moc.list());
        
  // Print the ASCII and JSON serializations of '2mass_inter_sdss12_d2'
  console.log(moc.toAscii('2mass_inter_sdss12_d2'));
  console.log(moc.toJson('2mass_inter_sdss12_d2'));
  
  // Save the result of the intersection in a FITS file
  moc.toFitsFile('2mass_inter_sdss12');
  return;
})();
      

Try copy/paste and exec the following lines of javascript to manipulate multi-order maps (no CORS on cdsxmatch, so the data URL works only if this page URL is on cdsxmatch)

var n;
(async () => {
  // Load a multi-order map and create a MOC on-the-fly
  await moc.fromMultiOrderMapFitsUrl('lalmap', 'http://cdsxmatch.u-strasbg.fr/lab/moc/LALInference.multiorder.fits', 0.0, 0.9, false, false, false, false);
  // List MOCs loaded in the page
  console.log(moc.list());

  // Init a timer
  console.time('timer');

  // Count the number of disjoint MOCs in the MOC
  n = moc.splitCount('lalmap');
  console.log("n sub_mocs: " + n);
  console.timeLog('timer', 'Spit count'); 

  // Do split the MOC in 10 sub-MOCs
  moc.split('lalmap', 'lalmap_sub');
  console.timeLog('timer', 'Spit'); 
  // Remove timer
  console.timeEnd('timer');

  // List MOCs loaded in the page
  console.log(moc.list()); 

  // Get info on sub-MOCs
  for (let i = 0; i < n; i++) {  
    console.log("Coverage percentage sub " + i  + ": " + moc.info("lalmap_sub_" + i).coverage_percentage);
  }
  return;
})();