I've created a function to add the cloud+shadow+snow percentage for a particular region as a new property so you can filter the image collection based on that new property.

// Function to add the cloud, shadow and snow percentge as a new property for each image. It uses 'QA_PIXEL' band

function add_cloudCover(img){ // Bit 3 - Cloud // Bit 4 - Cloud Shadow // Bit 5 - Snow var imagen = img var cloudsBitMask = 1 << 3; var cloudShadowBitMask = 1 << 4; var snowBitMask = 1 << 5; var qa = img.select('QA_PIXEL').clip(region); var unmasked = qa.gt(0) var unmasked_area = unmasked.multiply(ee.Image.pixelArea()); var mask = qa.bitwiseAnd(cloudShadowBitMask).eq(0) .and(qa.bitwiseAnd(cloudsBitMask).eq(0) .and(qa.bitwiseAnd(snowBitMask).eq(0))); var masked_area = mask.multiply(ee.Image.pixelArea()); var u_area = unmasked_area.reduceRegion({ reducer: ee.Reducer.sum(), geometry: region.geometry(), scale: 30, maxPixels: 1e10 }); var area = masked_area.reduceRegion({ reducer: ee.Reducer.sum(), geometry: region.geometry(), scale: 30, maxPixels: 1e10 }); var landCover = ee.Number(area.get('QA_PIXEL')).multiply(100).divide(ee.Number(u_area.get('QA_PIXEL'))); var cloudCover = ee.Number(100).subtract(landCover).round(); return img.set('CLOUD_SHADOW_SNOW_COVER_REGION', cloudCover); }

I've created the following function to add the cloud+shadow+snow percentage for a particular region as a new image property so you can filter the image collection based on that property. The 'region' in the function refers to your area of interest or aoi.

    // Function to add the cloud, shadow and snow percentge as a new property for each image. It uses 'QA_PIXEL' band
function add_cloudCover(img){
  // Bit 3 - Cloud
  // Bit 4 - Cloud Shadow
  // Bit 5 - Snow
  var cloudsBitMask = 1 << 3;
  var cloudShadowBitMask = 1 << 4;
  var snowBitMask = 1 << 5;
  var qa = img.select('QA_PIXEL').clip(region);
  var unmasked = qa.gt(0)
  var unmasked_area = unmasked.multiply(ee.Image.pixelArea());
  var mask = qa.bitwiseAnd(cloudShadowBitMask).eq(0)
    .and(qa.bitwiseAnd(cloudsBitMask).eq(0)
    .and(qa.bitwiseAnd(snowBitMask).eq(0)));
  var masked_area = mask.multiply(ee.Image.pixelArea());
  var u_area = unmasked_area.reduceRegion({
  reducer: ee.Reducer.sum(),
  geometry: region.geometry(),
  scale: 30,
  maxPixels: 1e10
  });
  var area = masked_area.reduceRegion({
  reducer: ee.Reducer.sum(),
  geometry: region.geometry(),
  scale: 30,
  maxPixels: 1e10
  });
  var landCover = ee.Number(area.get('QA_PIXEL')).multiply(100).divide(ee.Number(u_area.get('QA_PIXEL')));
  var cloudCover = ee.Number(100).subtract(landCover).round();
  return img.set('CLOUD_SHADOW_SNOW_COVER_REGION', cloudCover);
}