landsat 8 - Apply a cloud mask to a Landsat8 collection in Google Earth Engine - time series

I have tried to apply a cloud mask for a landsat 8 collection using code1, code2, and code3 but none will work.

code1 encounters the error of not working even after changing

var mask = img.select(['cfmask']).neq(4) to

var mask = img.select(['pizel_qa_bands']).neq(3)

code2 encounters the problem of not being a time series dataset. I want to be able to extract pixel values for each image over a period of time but this code only gives one output of pixel values.

and I can't adapt my script to code3.

Here is my script and all i want to do is remove the clouds and cloud cover from a Landsat8 image collection

var l8_mayo = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA')
  .filterDate('2000-01-01', '2018-12-31')
  .filter(ee.Filter.eq('WRS_PATH', 208))

  .filter(ee.Filter.eq('WRS_ROW', 23));

var visParams = {bands: ['B4', 'B3', 'B2'], max: 0.3};
Map.setCenter(-9, 53, 8);
Map.addLayer(l8_mayo, visParams, 'l8_mayo collection');`

Answer

code2 works. Adapt it properly with right parameters (Always check metadata):

var l8_mayo = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA')
  .filterDate('2000-01-01', '2018-12-31')
  .filter(ee.Filter.eq('WRS_PATH', 208))

  .filter(ee.Filter.eq('WRS_ROW', 23));

var visParams = {bands: ['B4', 'B3', 'B2'], max: 0.3};
Map.setCenter(-9, 53, 8);
Map.addLayer(l8_mayo, visParams, 'l8_mayo collection');

var getQABits = function(image, start, end, newName) {
    // Compute the bits we need to extract.
    var pattern = 0;
    for (var i = start; i <= end; i++) {

       pattern += Math.pow(2, i);
    }
    // Return a single band image of the extracted QA bits, giving the band
    // a new name.
    return image.select([0], [newName])
                  .bitwiseAnd(pattern)
                  .rightShift(start);
};

// A function to mask out cloudy pixels.

var cloud_shadows = function(image) {
  // Select the QA band.
  var QA = image.select(['BQA']);
  // Get the internal_cloud_algorithm_flag bit.
  return getQABits(QA, 7,8, 'Cloud_shadows').eq(1);
  // Return an image masking out cloudy areas.
};

// A function to mask out cloudy pixels.
var clouds = function(image) {

  // Select the QA band.
  var QA = image.select(['BQA']);
  // Get the internal_cloud_algorithm_flag bit.
  return getQABits(QA, 4,4, 'Cloud').eq(0);
  // Return an image masking out cloudy areas.
};

var maskClouds = function(image) {
  var cs = cloud_shadows(image);
  var c = clouds(image);

  image = image.updateMask(cs);
  return image.updateMask(c);
};

var l8_mayo_free = l8_mayo.map(maskClouds);

Map.addLayer(l8_mayo_free, visParams, 'l8_mayo collection without clouds');

Link: https://code.earthengine.google.com/44cb99f8210800462da56640a275e674

There are some areas with cloud borders in image collection. Is a very cloudy area. BQA isn't perfect