javascript - Need an alert on first log in -

i have requirement show alert box when user logs in first time.

i used localstorage method below:

var visited = localstorage.getitem('visited');  if (!visited) {     alert("please view firefox" + visited); } 

however, seems working, doesnot work on every login, works when page visited first time.

please let me know if there way it. please note, using javascript functionality done.

thanks, ark