GTM Sampling Variable

sampleId.js

function(){
  // Sets and gets a sample ID for bucket selection in A/B and related testing methodologies.
  
  var ckPattern = /sampleId=(\d+)/g;
  var sampleId = -1;
  
  // TODO: adopt a different method for selecting the corp top level domain
  var domain = document.location.hostname;
  
  document.cookie.replace(ckPattern, function($0, $d){
    sampleId = Number($d);
  });
  
  if (sampleId < 0){
    sampleId = (Math.random() * 1E10) >>> 0;
    document.cookie = ('sampleId=' + sampleId + '; path=/; domain=' + domain + ';');
  }
  
  return sampleId;
}

sampleSelection.js

function(){
  // Evaluate the sample ID into a specific bucket selection
  var sampleId = {{sampleId}}; 
  var limit = 100;
  var split = 70; // i.e. 30% are sampled as "true"
  return (Number(sampleId) % limit > split) ? 'true' : 'false';
}