You can use localStorage if available, and if it's not, then using cookies (or whatever you feel to):
var appToken = createToken();
try {
if (localStorage.getItem) {
localStorage.downloadAppAlert = appToken;
} else {
setCookie('downloadAppAlert', appToken, 10); // name, a string value, num. of days
}
} catch(e) {
console.log(e);
}
Then you can use some function to set your cookies - i.e. this one i just found in w3schools:
function setCookie(c_name,value,exdays)
{
var exdate=new Date();
exdate.setDate(exdate.getDate() + exdays);
var c_value=escape(value) + ((exdays==null) ? "" : "; expires="+exdate.toUTCString());
document.cookie=c_name + "=" + c_value;
}
To retrieve a cookie value by it's name - downloadAppAlert in the example - you can use the one on the w3schools link or something like this:
function readCookie(name) {
var nameEQ = name + '=';
var ca = document.cookie.split(';');
for(var i=0;i < ca.length;i++) {
var c = ca[i];
while (c.charAt(0)==' ') c = c.substring(1,c.length);
if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
}
return null;
}
Also, to retrieve a previously setted item on the localStorage you simply:
var appToken = localStorage.getItem('downloadAppAlert');
EDIT: Sorry, with the hurries i forgot to mention what createToken() does. It is supposed to be a random alphanumeric generator function. You can find plenty on SO, like:
Random alpha-numeric string in JavaScript?
Generate random string/characters in JavaScript
Generating (pseudo)random alpha-numeric strings
