I am using Dexie to access IndexedDB on a flash card maker project. I can manipulate the database as expected, and it stays in the database if I close and reopen the browser, but often when I open up the project after not working on it for a few days, the stored data I put into the database isn't there any longer.
I did some research and discovered that I need to make the database persistent, but I can't figure out how to do that.
I have pretty much copied the recommended code from the Dexie Storage Manager page into the onLoad function for the main page, index.js. Here is the relevant code:
//When the page loads, display the decks in ul on the webpage.
window.addEventListener('load', onLoad);
async function onLoad() {
//Check how much data is available.
showEstimatedQuota();
//Make sure the storage is persistent.
isStoragePersisted().then(async isPersisted => {
if (isPersisted) {
console.log(":) Storage is successfully persisted.");
} else {
console.log(":( Storage is not persisted.");
console.log("Trying to persist..:");
if (await persist()) {
console.log(":) We successfully turned the storage to be persisted.");
} else {
console.log(":( Failed to make storage persisted");
}
}
});
}
The above onLoad function references three functions I have saved on dexie-setup.js:
//This function makes the storage persistent.
//(Copied from https://dexie.org/docs/StorageManager)
async function persist() {
return await navigator.storage && navigator.storage.persist &&
navigator.storage.persist();
}
//This function checks if the storage is persistent.
//(Copied from https://dexie.org/docs/StorageManager)
async function isStoragePersisted() {
return await navigator.storage && navigator.storage.persisted &&
navigator.storage.persisted();
}
//This function logs to console how much data is available.
//(Copied from https://dexie.org/docs/StorageManager)
async function showEstimatedQuota() {
if (navigator.storage && navigator.storage.estimate) {
const estimation = await navigator.storage.estimate();
console.log(`Quota: ${estimation.quota}`);
console.log(`Usage: ${estimation.usage}`);
} else {
console.error("StorageManager not found");
}
}
My console logs:
dexie-setup.js:56 Quota: 6358499328
dexie-setup.js:57 Usage: 25370
index.js:30 :( Storage is not persisted.
index.js:31 Trying to
persist..:
dexie-setup.js:84 Done checking dexie.
index.js:33 :) We successfully turned the storage to be persisted.
However, if I refresh the page, I get the same thing logged on my console: the database is still set to not persistent.
The showEstimatedQuota function checks the data storage and confirms that the DataStorage API is functioning, so I don't think that's the problem. (I'm only storing small objects with text in them, so I don't expect to exceed the storage limit, anyway.)
So far, the project is entirely local on my chromebook, and I am viewing it on a Chrome browser.
Please let me know how to make my database persistent. I'm pretty new to this (this is my first question on stackoverflow!), so hopefully it's an easy problem to solve! Thanks in advance.
citing the documentation of Dexie: "Even though IndexedDB is a fully functional client-side database for the web, it is not a persistent storage by default. IndexedDB without StorageManager is just a “best-effort” database that can be erased in situations of low disk space on a device. The browser may delete your database without notifying the user in case it needs to free up space for other website’s data that was used more recently than yours."
So, you can't make the database persistent. Just make a “best-effort”.
This links can be of help:
https://web.dev/persistent-storage/
Chrome.Storage.Local Persistence
I hope it will be of help to you.
The only way I have found is that if the user bookmarks the site then it enables persistent storage using the persist function:
//This function makes the storage persistent.
//(Copied from https://dexie.org/docs/StorageManager)
async function persist() {
return await navigator.storage && navigator.storage.persist &&
navigator.storage.persist();
}
So you may prompt the user to bookmark your site when it loads.
I have one html page 1.html and i want to get some text content and store it to a js.js file using jquery to get the text by id.
This code only works in 1.html page, where the text I want to copy from is but not in 2.html file.
Here is my code. Note that it works if I store text inside localstorage setter second parameter.
$( document ).ready(function() {
var c1Title= $('#r1c1Title').text();
//changing c1Title to any String content like "test" will work
localStorage.setItem("t1",c1Title);
var result = localStorage.getItem("t1");
$("#title1").html(result);
alert(result);
});
Here is the complete demo I am working on Github:
You need to use either localStorage or cookies.
With localStorage
On the first page, use the following code:
localStorage.setItem("variableName", "variableContent")
That sets a localStorage variable of variableName for the domain, with the content variableContent. You can change these names and values to whatever you want, they are just used as an example
On the second page, get the value using the following code:
localStorage.getItem("variableName")
That will return the value stored in variableName, which is variableContent.
Notes
There is a 5MB limit on the amount of data you can store in localStorage.
You can remove items using localStorage.removeItem("variableName").
Depending on where you are, you may need to take a look at the cookie policy (this effects all forms of websites storing data on a computer, not just cookies). This is important, as otherwise using any of these solutions may be illegal.
If you only want to store data until the user closes their browser, you can use sessionStorage instead (just change localStorage to sessionStorage in all instances of your code)
If you want to be able to use the variable value on the server as well, use cookies instead - check out cookies on MDN
For more information on localStorage, check out this article on MDN, or this one on W3Schools
Please try to use this code. It's better to use local storage.
Here you need to make sure that you are setting this local storage
value in parent html page or parent js file.
create local storage
localStorage.setItem("{itemlable}", {itemvalue});
localStorage.setItem("variable1", $('#r1c1Title').text());
localStorage.setItem("variable2", $('#r1c2Title').text());
Get local storage value
localStorage.getItem("{itemlable}")
alert(localStorage.getItem("variable1") + ' Second variable ::: '+ localStorage.getItem("variable2"));
For more information follow this link https://www.w3schools.com/html/html5_webstorage.asp
If you wanted to store in div then follow this code.
Html Code
<div class="div_data"></div>
Js code:
$(document).ready(function () {
localStorage.setItem("variable1", "Value 1");
localStorage.setItem("variable2", "Value 2");
$(".div_data").html(' First variable ::: '+localStorage.getItem("variable1") + ' Second variable ::: '+ localStorage.getItem("variable2"));
});
Hope this helps.
You can use local storage as mentioned in above comments. Please find below how to write in javascript.
Local Storage Pros and Cons
Pros:
Web storage can be viewed simplistically as an improvement on cookies, providing much greater storage capacity.
5120KB (5MB which equals 2.5 Million chars on Chrome) is the default storage size for an entire domain.
This gives you considerably more space to work with than a typical 4KB cookie.
The data is not sent back to the server for every HTTP request (HTML, images, JavaScript, CSS, etc) - reducing the amount of traffic between client and server.
The data stored in localStorage persists until explicitly deleted. Changes made are saved and available for all current and future visits to the site.
Cons:
It works on same-origin policy. So, data stored will only be available on the same origin.
// Store value in local storage
localStorage.setItem("c1Title", $('#r1c1Title').text());
// Retrieve value in local storage
localStorage.getItem("c1Title");
Your html div
<div id="output"></div>
Add Javascript Code
$('#output').html(localStorage.getItem("c1Title"));
Let me know if it not works
Create a common.js file and modified this and save.
Session = (function () {
var instance;
function init() {
var sessionIdKey = "UserLoggedIn";
return {
// Public methods and variables.
set: function (sessionData) {
window.localStorage.setItem(sessionIdKey, JSON.stringify(sessionData));
return true;
},
get: function () {
var result = null;
try {
result = JSON.parse(window.localStorage.getItem(sessionIdKey));
} catch (e) { }
return result;
}
};
};
return {
getInstance: function () {
if (!instance) {
instance = init();
}
return instance;
}
};
}());
function isSessionActive() {
var session = Session.getInstance().get();
if (session != null) {
return true;
}
else {
return false;
}
}
function clearSession() {
window.localStorage.clear();
window.localStorage.removeItem("CampolUserLoggedIn");
window.location.assign("/Account/Login.aspx");
}
Insert like this.
$(function () {
if (!isSessionActive()) {
var obj = {};
obj.ID = 1;
obj.Name = "Neeraj Pathak";
obj.OrganizationID = 1;
obj.Email = "npathak56#gmail.com";
Session.getInstance().set(obj);
}
///clearSession();
});
get like this way
LoggedinUserDetails = Session.getInstance().get();
Okay. So i have heard plenty about building apps using phonegap and html5. the app works fine but it access a web service to populate the div for display. The service runs well what i want to implement is a caching mechanism for storing the last interface from the service using local-storage while a fresh request is going on in the background.
This is my javascript code. Please what am i doing wrong.
P.S am a html5/js intermediate user. However, i user php really well.
function loadHome()
{
$("#post_display").html(waitText);
$.get(api_url',{ app_key: my_app_key } ,
function(data){
if(('localStorage' in window) && window['localStorage'] !== null)
{
localStorage.setItem('data_home',data); alert(localStorage.getItem(data_home));
}
$("#post_display").html(data) }
);
}
so far, the alert works and shows me the data stored. Now how do i display the data when the user returns to the page. what conditional logic do i use?
sample
if(localstorage.data_home){ //display store data here }
else{//run the ajax call to the api service}
i dont know how to go about this. Help.
just check before you call ajax. It's just a sample, you need to refact your source code.
function loadHome()
{
$("#post_display").html(waitText);
if(('localStorage' in window) && window['localStorage'] !== null && localStorage.getItem('data_home')){
$("#post_display").html(localStorage.getItem('data_home'));
return;
}
$.get(api_url',{ app_key: my_app_key } ,
function(data){
if(('localStorage' in window) && window['localStorage'] !== null)
{
localStorage.setItem('data_home',data); alert(localStorage.getItem(data_home));
}
$("#post_display").html(data) }
);
}
My Case: localStorage with key + value that should be deleted when browser is closed and not single tab.
Please see my code if its proper and what can be improved:
//create localStorage key + value if not exist
if (localStorage) {
localStorage.myPageDataArr = {
"name" => "Dan",
"lastname" => "Bonny"
};
}
//when browser closed - psedocode
$(window).unload(function() {
localStorage.myPageDataArr = undefined;
});
should be done like that and not with delete operator:
localStorage.removeItem(key);
Use with window global keyword:-
window.localStorage.removeItem('keyName');
You should use the sessionStorage instead if you want the key to be deleted when the browser close.
You can make use of the beforeunload event in JavaScript.
Using vanilla JavaScript you could do something like:
window.onbeforeunload = function() {
localStorage.removeItem(key);
return '';
};
That will delete the key before the browser window/tab is closed and prompts you to confirm the close window/tab action. I hope that solves your problem.
NOTE: The onbeforeunload method should return a string.
localStorage.removeItem(key); //item
localStorage.clear(); //all items
There is a very specific use case in which any suggestion to use sessionStorage instead of localStorage does not really help.
The use-case would be something as simple as having something stored while you have at least one tab opened, but invalidate it if you close the last tab remaining.
If you need your values to be saved cross-tab and window, sessionStorage does not help you unless you complicate your life with listeners, like I have tried.
In the meantime localStorage would be perfect for this, but it does the job 'too well', since your data will be waiting there even after a restart of the browser.
I ended up using a custom code and logic that takes advantage of both.
I'd rather explain then give code. First store what you need to in localStorage, then also in localStorage create a counter that will contain the number of tabs that you have opened.
This will be increased every time the page loads and decreased every time the page unloads. You can have your pick here of the events to use, I'd suggest 'load' and 'unload'.
At the time you unload, you need to do the cleanup tasks that you'd like to when the counter reaches 0, meaning you're closing the last tab.
Here comes the tricky part: I haven't found a reliable and generic way to tell the difference between a page reload or navigation inside the page and the closing of the tab.
So If the data you store is not something that you can rebuild on load after checking that this is your first tab, then you cannot remove it at every refresh.
Instead you need to store a flag in sessionStorage at every load before increasing the tab counter.
Before storing this value, you can make a check to see if it already has a value and if it doesn't,
this means you're loading into this session for the first time, meaning that you can do the cleanup at load if this value is not set and the counter is 0.
use sessionStorage
The sessionStorage object is equal to the localStorage object, except that it stores the data for only one session. The data is deleted when the user closes the browser window.
The following example counts the number of times a user has clicked a button, in the current session:
Example
if (sessionStorage.clickcount) {
sessionStorage.clickcount = Number(sessionStorage.clickcount) + 1;
} else {
sessionStorage.clickcount = 1;
}
document.getElementById("result").innerHTML = "You have clicked the button " +
sessionStorage.clickcount + " time(s) in this session.";
Try using
$(window).unload(function(){
localStorage.clear();
});
Hope this works for you
There are five methods to choose from:
setItem(): Add key and value to localStorage
getItem(): Retrieve a value by the key from localStorage
removeItem(): Remove an item by key from localStorage
clear(): Clear all localStorage
key(): Passed a number to retrieve nth key of a localStorage
You can use clear(), this method when invoked clears the entire storage of all records for that domain. It does not receive any parameters.
window.localStorage.clear();
for (let i = 0; i < localStorage.length; i++) {
if (localStorage.key(i).indexOf('the-name-to-delete') > -1) {
arr.push(localStorage.key(i));
}
}
for (let i = 0; i < arr.length; i++) {
localStorage.removeItem(arr[i]);
}
8.5 years in and the original question was never actually answered.
when browser is closed and not single tab.
This basic code snippet will give you the best of both worlds. Storage that persists only as long as the browser session (like sessionStorage), but is also shareable between tabs (localStorage).
It does this purely through localStorage.
function cleanup(){
// place whatever cleanup logic you want here, for example:
// window.localStorage.removeItem('my-item')
}
function tabOpened(){
const tabs = JSON.parse(window.localStorage.getItem('tabs'))
if (tabs === null) {
window.localStorage.setItem('tabs', 1)
} else {
window.localStorage.setItem('tabs', ++tabs)
}
}
function tabClosed(){
const tabs = JSON.parse(window.localStorage.getItem('tabs'))
if (tabs === 1) {
// last tab closed, perform cleanup.
window.localStorage.removeItem('tabs')
cleanup()
} else {
window.localStorage.setItem('tabs', --tabs)
}
}
window.onload = function () {
tabOpened();
}
window.onbeforeunload = function () {
tabClosed();
}
why not used sessionStorage?
"The sessionStorage object is equal to the localStorage object, except that it stores the data for only one session. The data is deleted when the user closes the browser window."
http://www.w3schools.com/html/html5_webstorage.asp
Although, some users already answered this question already, I am giving an example of application settings to solve this problem.
I had the same issue. I am using https://github.com/grevory/angular-local-storage module in my angularjs application. If you configure your app as follows, it will save variable in session storage instead of local storage. Therefore, if you close the browser or close the tab, session storage will be removed automatically. You do not need to do anything.
app.config(function (localStorageServiceProvider) {
localStorageServiceProvider
.setPrefix('myApp')
.setStorageType('sessionStorage')
});
Hope it will help.
Here's a simple test to see if you have browser support when working with local storage:
if(typeof(Storage)!=="undefined") {
console.log("localStorage and sessionStorage support!");
console.log("About to save:");
console.log(localStorage);
localStorage["somekey"] = 'hello';
console.log("Key saved:");
console.log(localStorage);
localStorage.removeItem("somekey"); //<--- key deleted here
console.log("key deleted:");
console.log(localStorage);
console.log("DONE ===");
} else {
console.log("Sorry! No web storage support..");
}
It worked for me as expected (I use Google Chrome).
Adapted from: http://www.w3schools.com/html/html5_webstorage.asp.
I don't think the solution presented here is 100% correct because window.onbeforeunload event is called not only when browser/Tab is closed(WHICH IS REQUIRED), but also on all other several events. (WHICH MIGHT NOT BE REQUIRED)
See this link for more information on list of events that can fire window.onbeforeunload:-
http://msdn.microsoft.com/en-us/library/ms536907(VS.85).aspx
After looking at this question 6 years after it was asked, I found that there still is no sufficient answer to this question; which should achieve all of the following:
Clear Local Storage after closing the browser (or all tabs of the domain)
Preserve Local Storage across tabs, if at least one tab remains active
Preserve Local Storage when reloading a single tab
Execute this piece of javascript at the start of each page load in order to achieve the above:
((nm,tm) => {
const
l = localStorage,
s = sessionStorage,
tabid = s.getItem(tm) || (newid => s.setItem(tm, newid) || newid)((Math.random() * 1e8).toFixed()),
update = set => {
let cur = JSON.parse(l.getItem(nm) || '{}');
if (set && typeof cur[tabid] == 'undefined' && !Object.values(cur).reduce((a, b) => a + b, 0)) {
l.clear();
cur = {};
}
cur[tabid] = set;
l.setItem(nm, JSON.stringify(cur));
};
update(1);
window.onbeforeunload = () => update(0);
})('tabs','tabid');
Edit: The basic idea here is the following:
When starting from scratch, the session storage is assigned a random id in a key called tabid
The local storage is then set with a key called tabs containing a object those key tabid is set to 1.
When the tab is unloaded, the local storage's tabs is updated to an object containing tabid set to 0.
If the tab is reloaded, it's first unloaded, and resumed. Since the session storage's key tabid exists, and so does the local storage tabs key with a sub-key of tabid the local storage is not cleared.
When the browser is unloaded, all session storage will be cleared. When resuming the session storage tabid won't exists anymore and a new tabid will be generated. Since the local storage does not have a sub-key for this tabid, nor any other tabid (all session were closed), it's cleared.
Upon a new created tab, a new tabid is generated in session storage, but since at least one tabs[tabid] exists, the local storage is not cleared
This will do the trick for objects.
localStorage.removeItem('key');
Or
localStorage.setItem('key', 0 );
You can simply use sessionStorage. Because sessionStorage allow to clear all key value when browser window will be closed .
See there : SessionStorage- MDN
This is an old question, but it seems none of the answer above are perfect.
In the case you want to store authentication or any sensitive information that are destructed only when the browser is closed, you can rely on sessionStorage and localStorage for cross-tab message passing.
Basically, the idea is:
You bootstrap from no previous tab opened, thus both your localStorage and sessionStorage are empty (if not, you can clear the localStorage). You'll have to register a message event listener on the localStorage.
The user authenticate/create a sensitive info on this tab (or any other tab opened on your domain).
You update the sessionStorage to store the sensitive information, and use the localStorage to store this information, then delete it (you don't care about timing here, since the event was queued when the data changed). Any other tab opened at that time will be called back on the message event, and will update their sessionStorage with the sensitive information.
If the user open a new tab on your domain, its sessionStorage will be empty. The code will have to set a key in the localStorage (for exemple: req). Any(all) other tab will be called back in the message event, see that key, and can answer with the sensitive information from their sessionStorage (like in 3), if they have such.
Please notice that this scheme does not depend on window.onbeforeunload event which is fragile (since the browser can be closed/crashed without these events being fired). Also, the time the sensitive information is stored on the localStorage is very small (since you rely on transcients change detection for cross tab message event) so it's unlikely that such sensitive information leaks on the user's hard drive.
Here's a demo of this concept: http://jsfiddle.net/oypdwxz7/2/
There are no such the way to detect browser close so probably you can't delete localStorage on browser close but there are another way to handle the things you can uses sessionCookies as it will destroy after browser close.This is I implemented in my project.
if(localStorage.getItem("visit") === null) {
localStorage.setItem('visit', window.location.hostname);
console.log(localStorage.getItem('visit'));
}
else if(localStorage.getItem('visit') == 'localhost'){
console.log(localStorage.getItem('visit'));
}
else {
console.log(localStorage.getItem('visit'));
}
$(document).ready(function(){
$("#clickme").click(function(){
localStorage.setItem('visit', '0');
});
});
window.localStorage.removeItem('visit');
window.addEventListener('beforeunload', (event) => {
localStorage.setItem("new_qus_id", $('.responseId').attr('id'));
var new_qus_no = localStorage.getItem('new_qus_id');
console.log(new_qus_no);
});
if (localStorage.getItem('new_qus_id') != '') {
var question_id = localStorage.getItem('new_qus_id');
} else {
var question_id = "<?php echo $question_id ; ?>";
}
you can try following code to delete local storage:
delete localStorage.myPageDataArr;
I have a notes box that can be used to store notes, originally I was using cookies to store the entries, then I tried HTML5 Storage and I can't get it to work, here is the code:
$(document).ready(function () {
$('#savesNotes').click(function () {
localStorage.nltwonotes=document.forms[0].todo1.value;
}
});
document.forms[0].todo1.value=localStorage.nltwonotes;
});
Here is some working code:
Preview (type in, then view your localStorage in your console) :
http://jsbin.com/exote5/
Source:
http://jsbin.com/exote5/edit
$(document).ready(function () {
$('#saveNotes').click(function () {
localStorage.nltwonotes=$('#note').val();
});
if(localStorage.nltwonotes){
$('#note').val(localStorage.nltwonotes);
}
else{
//Not set yet
}
});
== NOTE ABOUT THE FILE:/// PROTOCOL ==
You must have localStorage on a server (http or https). Firefox will not let you use them locally. If you are using a Mac you can use MAMP or on Windows you can use WAMP If you're on Linux you probably already know how to setup a local hosting enviroment with apache which is usually provided...
I'd recommend using the methods provided to access localStorage instead of how you're doing it:
localStorage.setItem("nltwonotes", document.forms[0].todo1.value);
Then to get a value:
document.forms[0].todo1.value = localStorage.getItem("nltwonotes");
Though, make sure you check to see if localStorage is even available:
function supports_html5_storage() {
try {
return 'localStorage' in window && window['localStorage'] !== null;
} catch (e) {
return false;
}
}
Otherwise you'll want to fallback / tell the user to upgrade their browser to one that supports local storage.