For how long is data stored in localStorage (as part of DOM Storage in HTML5) available? Can I set an expiration time for the data which I put into local storage?
This question is related to
javascript
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local-storage
You can use lscache. It handles this for you automatically, including instances where the storage size exceeds the limit. If that happens, it begins pruning items that are the closest to their specified expiration.
From the readme:
lscache.set
Stores the value in localStorage. Expires after specified number of minutes.
Arguments
key (string)
value (Object|string)
time (number: optional)
This is the only real difference between the regular storage methods. Get, remove, etc work the same.
If you don't need that much functionality, you can simply store a time stamp with the value (via JSON) and check it for expiry.
Noteworthy, there's a good reason why local storage is left up to the user. But, things like lscache do come in handy when you need to store extremely temporary data.
// Functions
function removeHtmlStorage(name) {
localStorage.removeItem(name);
localStorage.removeItem(name+'_time');
}
function setHtmlStorage(name, value, expires) {
if (expires==undefined || expires=='null') { var expires = 3600; } // default: 1h
var date = new Date();
var schedule = Math.round((date.setSeconds(date.getSeconds()+expires))/1000);
localStorage.setItem(name, value);
localStorage.setItem(name+'_time', schedule);
}
function statusHtmlStorage(name) {
var date = new Date();
var current = Math.round(+date/1000);
// Get Schedule
var stored_time = localStorage.getItem(name+'_time');
if (stored_time==undefined || stored_time=='null') { var stored_time = 0; }
// Expired
if (stored_time < current) {
// Remove
removeHtmlStorage(name);
return 0;
} else {
return 1;
}
}
// Status
var cache_status = statusHtmlStorage('cache_name');
// Has Data
if (cache_status == 1) {
// Get Cache
var data = localStorage.getItem('cache_name');
alert(data);
// Expired or Empty Cache
} else {
// Get Data
var data = 'Pay in cash :)';
alert(data);
// Set Cache (30 seconds)
if (cache) { setHtmlStorage('cache_name', data, 30); }
}
If you’re familiar with the browsers locaStorage object, you know that there’s no provision for providing an expiry time. However, we can use Javascript to add a TTL (Time to live) to invalidate items in locaStorage after a certain period of time elapses.
function setLocalStorageItem(key, value, ttl) {
// `item` is an object which contains the original value
// as well as the time when it's supposed to expire
let item = {
value: value,
expiry: ttl ? Date.now() + ttl : null
};
localStorage.setItem(key, JSON.stringify(item));
}
function getLocalStorageItem(key) {
let item = localStorage.getItem(key);
// if the item doesn't exist, return null
if (!item) return null;
item = JSON.parse(item);
// compare the expiry time of the item with the current time
if (item.expiry && Date.now() > item.expiry) {
// If the item is expired, delete the item from storage and return null
localStorage.removeItem(key);
return null;
}
return item.value;
}
Workaround using angular and localforage:
angular.module('app').service('cacheService', function() {
return {
set: function(key, value, expireTimeInSeconds) {
return localforage.setItem(key, {
data: value,
timestamp: new Date().getTime(),
expireTimeInMilliseconds: expireTimeInSeconds * 1000
})
},
get: function(key) {
return localforage.getItem(key).then(function(item) {
if(!item || new Date().getTime() > (item.timestamp + item.expireTimeInMilliseconds)) {
return null
} else {
return item.data
}
})
}
}
})
You can try this one.
var hours = 24; // Reset when storage is more than 24hours
var now = Date.now();
var setupTime = localStorage.getItem('setupTime');
if (setupTime == null) {
localStorage.setItem('setupTime', now)
} else if (now - setupTime > hours*60*60*1000) {
localStorage.clear()
localStorage.setItem('setupTime', now);
}
@sebarmeli's approach is the best in my opinion, but if you only want data to persist for the life of a session then sessionStorage is probably a better option:
This is a global object (sessionStorage) that maintains a storage area that's available for the duration of the page session. A page session lasts for as long as the browser is open and survives over page reloads and restores. Opening a page in a new tab or window will cause a new session to be initiated.
For the benefit of searchers:
Like Fernando, I didn't want to add a load of json when the values stored were simple. I just needed to track some UI interaction and keep the data relevant (e.g. how a user used an ecommerce site before checking out).
This will not meet everyones criteria, but will hopefully be a quick copy+paste starter for someone and save adding another lib.
NOTE: This would not be good if you need to retrieve the items individually.
// Addition
if(window.localStorage){
localStorage.setItem('myapp-' + new Date().getTime(), 'my value');
}
// Removal of all expired items
if(window.localStorage){
// two mins - (1000 * 60 * 20) would be 20 mins
var expiryTime = new Date().getTime() - (1000 * 60 * 2);
var deleteRows = [];
for(var i=0; i < localStorage.length; i++){
var key = localStorage.key(i);
var partsArray = key.split('-');
// The last value will be a timestamp
var lastRow = partsArray[partsArray.length - 1];
if(lastRow && parseInt(lastRow) < expiryTime){
deleteRows.push(key);
}
}
// delete old data
for(var j=0; j < deleteRows.length; j++){
localStorage.removeItem(deleteRows[j]);
}
}
While local storage does not supply an expiration mechanism, cookies do. Simply pairing a local storage key with a cookie provides an easy way to ensure that local storage can be updated with the same expiration parameters as a cookie.
Example in jQuery:
if (!$.cookie('your_key') || !localStorage.getItem('your_key')) {
//get your_data from server, then...
localStorage.setItem('your_key', 'your_data' );
$.cookie('your_key', 1);
} else {
var your_data = localStorage.getItem('your_key');
}
// do stuff with your_data
This example sets a cookie with the default parameter to expire when the browser is closed. Thus, when the browser is closed and re-opened, the local data store for your_data gets refreshed by a server-side call.
Note that this is not exactly the same as removing the local data store, it is instead updating the local data store whenever the cookie expires. However, if your main goal is to be able to store more than 4K client-side (the limitation for cookie size), this pairing of cookie and local storage will help you to accomplish a larger storage size using the same expiration parameters as a cookie.
The lifecycle is controlled by the application/user.
From the standard:
User agents should expire data from the local storage areas only for security reasons or when requested to do so by the user. User agents should always avoid deleting data while a script that could access that data is running.
I would suggest to store timestamp in the object you store in the localStorage
var object = {value: "value", timestamp: new Date().getTime()}
localStorage.setItem("key", JSON.stringify(object));
You can parse the object, get the timestamp and compare with the current Date, and if necessary, update the value of the object.
var object = JSON.parse(localStorage.getItem("key")),
dateString = object.timestamp,
now = new Date().getTime().toString();
compareTime(dateString, now); //to implement
If someone using jStorage Plugin of jQuery the it can be add expiry with setTTL function if jStorage plugin
$.jStorage.set('myLocalVar', "some value");
$.jStorage.setTTL("myLocalVar", 24*60*60*1000); // 24 Hr.
Brynner Ferreira, has brought a good point: storing a sibling key where expiration info resides. This way, if you have a large amount of keys, or if your values are large Json objects, you don't need to parse them to access the timestamp.
here follows an improved version:
/* removeStorage: removes a key from localStorage and its sibling expiracy key
params:
key <string> : localStorage key to remove
returns:
<boolean> : telling if operation succeeded
*/
function removeStorage(name) {
try {
localStorage.removeItem(name);
localStorage.removeItem(name + '_expiresIn');
} catch(e) {
console.log('removeStorage: Error removing key ['+ key + '] from localStorage: ' + JSON.stringify(e) );
return false;
}
return true;
}
/* getStorage: retrieves a key from localStorage previously set with setStorage().
params:
key <string> : localStorage key
returns:
<string> : value of localStorage key
null : in case of expired key or failure
*/
function getStorage(key) {
var now = Date.now(); //epoch time, lets deal only with integer
// set expiration for storage
var expiresIn = localStorage.getItem(key+'_expiresIn');
if (expiresIn===undefined || expiresIn===null) { expiresIn = 0; }
if (expiresIn < now) {// Expired
removeStorage(key);
return null;
} else {
try {
var value = localStorage.getItem(key);
return value;
} catch(e) {
console.log('getStorage: Error reading key ['+ key + '] from localStorage: ' + JSON.stringify(e) );
return null;
}
}
}
/* setStorage: writes a key into localStorage setting a expire time
params:
key <string> : localStorage key
value <string> : localStorage value
expires <number> : number of seconds from now to expire the key
returns:
<boolean> : telling if operation succeeded
*/
function setStorage(key, value, expires) {
if (expires===undefined || expires===null) {
expires = (24*60*60); // default: seconds for 1 day
} else {
expires = Math.abs(expires); //make sure it's positive
}
var now = Date.now(); //millisecs since epoch time, lets deal only with integer
var schedule = now + expires*1000;
try {
localStorage.setItem(key, value);
localStorage.setItem(key + '_expiresIn', schedule);
} catch(e) {
console.log('setStorage: Error setting key ['+ key + '] in localStorage: ' + JSON.stringify(e) );
return false;
}
return true;
}
From the W3C draft:
User agents should expire data from the local storage areas only for security reasons or when requested to do so by the user. User agents should always avoid deleting data while a script that could access that data is running.
You'll want to do your updates on your schedule using setItem(key, value); that will either add or update the given key with the new data.
If anyone still looking for a quick solution and don't want dependencies like jquery etc I wrote a mini lib that add expiration to local / session / custom storage, you can find it with source here:
Here highly recommended to use sessionStorage
for set value use
sessionStorage.setItem("key","my value");
for get value use
var value = sessionStorage.getItem("key");
all ways for set are
sessionStorage.key = "my val";
sessionStorage["key"] = "my val";
sessionStorage.setItem("key","my value");
all ways for get are
var value = sessionStorage.key;
var value = sessionStorage["key"];
var value = sessionStorage.getItem("key");
Source: Stackoverflow.com