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Stores a copy of tealium_visitor_id in local storage
/*
*
* Summary: Copies Tealium visitor id cookie value to localStorage to create a more
* durable anonymous visitor id.
*
* Requirements:
* - This localStorage value will not be updated until the 1 year point
* - This JS Code below is copy/pasted to a JavaScript Extension in Tealium iQ
* with an "All Tags" scope
*
* Note:
* - Many vendors support mapping of visitor id, use the tealium_visitor_id for
* mapping to override each vendor's visitor id (configure mapping where needed).
* - This solution does not attempt to write back over the current cookie value that
* may contain a different tealium_visitor_id. Code shows how to update the
* tealium_visitor_id to default to the value retrieved from localStorage. The data
* layer would then contain the most-likely-to-be-consistent value.
* - While this technique can be used for more than just an anonymous id, remember
* that any PII information is best kept out of client-side cookies and localStorage
*
*/
// This string used for localStorage key as well as attribute name in data layer object
var localStorageKey = "teal_vid2";
// Update '365' number below to persist visitor id shorter/longer than 1 year
var durationInMS = 365*24*60*60*1000;
function getVisitorIdFromLocalStorage(){
var val = localStorage.getItem(localStorageKey);
return val || "";
}
/*
* Format of value in localStorage is 1551462917775_1551a323423465325235aafbe29177fe75
* (the timestamp of when it was written, followed by "_", followed by visitor id)
*/
function copyVisitorIdToLocalStorage(visitorId) {
var currentTime = new Date().getTime(),
timeWritten,
temp;
/*
* If the time elapsed is greater than duration, then overwrite with new id
* OR, if it is empty, then set for the first time
*/
temp = getVisitorIdFromLocalStorage();
timeWritten = parseInt(temp.split("_")[0] || 0);
if (temp === "" || (currentTime - timeWritten) > durationInMS) {
localStorage.setItem(localStorageKey, currentTime + "_" + visitorId);
}
}
// The b object is a reference to current data layer
copyVisitorIdToLocalStorage(b.tealium_visitor_id);
b[localStorageKey] = getVisitorIdFromLocalStorage();
/*
* If you want to always default to use the value in localStorage for visitor id, then
* keep the following line below:
*/
b.tealium_visitor_id = b[localStorageKey] || b.tealium_visitor_id;
@tygavin
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tygavin commented Oct 14, 2019

It appears localStorage is now limited similar to Cookies in Safari. Reference: https://webkit.org/blog/9521/intelligent-tracking-prevention-2-3/

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