setLocalStorage.js

var minBrowserVersions = {"safari":12.1,"ff":67.0};
function getCookie(cname) {
  var name = cname + "=";
  var decodedCookie = decodeURIComponent(document.cookie);
  var ca = decodedCookie.split(';');
  for(var i = 0; i <ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) == ' ') {
      c = c.substring(1);
    }
    if (c.indexOf(name) == 0) {
      return c.substring(name.length, c.length);
    }
  }
  return false;
}
function setCookie(cname, cvalue, exdays) {
  var d = new Date();
  d.setTime(d.getTime() + (exdays*24*60*60*1000));
  var expires = "expires="+ d.toUTCString();
  document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
}
function setLocalStorageFromCookie(){ 
  var value = {
    id: getCookie("optimizelyEndUserId"),
    set_time: Date.now() 
  };
  var string_value = JSON.stringify(value);
  localStorage.setItem("optimizelyEndUserId",string_value);
}
function checkBrowserVersion(minVersions){
  var curBrowser = optimizely.get('visitor').browserId;
  var curVersion = parseFloat(optimizely.get('visitor').browserVersion);
  if(minBrowserVersions[curBrowser] && curVersion >= minBrowserVersions[curBrowser]){
    console.log('Included browser');
    return true;
  }
  else{
  console.log('not applicable');
  }
}
function onActivated(){
  var matchingBrowser = checkBrowserVersion(minBrowserVersions);
  if(matchingBrowser){
     setLocalStorageFromCookie();
     }
};
function checkForAndSetId(cookieName){
  if(!getCookie(cookieName) && typeof localStorage.getItem(cookieName) != "undefined"){
        var value = JSON.parse(localStorage.getItem(cookieName));
        setCookie('optimizelyEndUserId',value.id,7);
  }
  else{
    window["optimizely"] = window["optimizely"] || [];
    window["optimizely"].push({
      type: "addListener",
      filter: {
        type: "lifecycle",
        name: "activated"
      },
      handler: onActivated
    });
  }
} 
checkForAndSetId("optimizelyEndUserId");