Init localStorage after every refresh - javascript

I would like to initialize localStorage object every time a user does a refresh by F-5.
Can i do such a thing?
The localStorage object is working fine by setItem and getItem methods.
However, I would like to know if i have the option to init this object every refresh action.
For example:
I have two different pages in my app. A.js and B.js.
When loading B.js i set the localStorage:
var id = getId();
window.localStorage.setItem("Id", id );
After that when i clicking on a button for going to A.js i am doing:
var selectedId = window.localStorage.getItem("Id");
if (selectedId !== null){
var intSelectedId = parseInt(selectedId );
//DO LOGIC
}
I would like to delete ("Id", id) key-value pair every refresh.
How can i do it?

Maybe like this ?
//declare in global scope
var myinitvalue = "blah";
//handle what happens just before page unloads
window.onbeforeunload = function() {
window.localStorage.setItem("Id", myinitvalue);
}
Unfortunately the side effect of this is that the value will also reset if browser tab is closed or if back button is clicked.

If you want to delete item with key Id once your page is loaded, do
window.onload=function(){
localStorage.removeItem("Id");
}

Related

How can I create a dynamic product page using HTML, CSS, and Javascript

I currently only know javascript. But the thing is I looked up how to do it and some people talk about something called localStorage. I have tried this and for some reason when I jump to a new page those variables aren't kept. Maybe I am doing something wrong? I jump to a new page via
and all I want do do is select a certain image. take that image to a new page and add it to that page.
I tried using the localStorage variables and even turning it into JSON.stringify and doing JSON.parse when trying to call the localstorage to another script. It didn't seem to work for me. Is there another solution?
This is some of my code. There are two scripts.
document.querySelectorAll(".card").forEach(item => {
item.addEventListener("click", onProductClick);
})
var div;
var productImg;
var ratingElement;
var reviewCount;
var price;
function onProductClick(){
// This took a week to find out (this.id)
// console.log(this.id);
div = document.getElementById(this.id);
productImg = div.getElementsByTagName('img')[0];
ratingElement = div.getElementsByTagName('a')[2];
reviewCount = div.getElementsByTagName('a')[3]
price = div.getElementsByTagName('a')[4];
console.log(div.getElementsByTagName('a')[4]);
var productData = [div, productImg,ratingElement,reviewCount,price];
window.localStorage.setItem("price", JSON.stringify(price));
}
function TranslateProduct(){
console.log("Hello");
}
This is script 2
var productPageImage = document.getElementById("product-image");
var myData = localStorage['productdata-local'];
var value =JSON.parse(window.localStorage.getItem('price'));
console.log(value);
// function setProductPage(img){
// if(productImg != null){
// return;
// }
// console.log(window.price);
// }
To explain my thought process on this code in the first script I have multiple images that have event listeners for a click. I wanted to Click any given image and grab all the data about it and the product. Then I wanted to move that to another script (script 2) and add it to a dynamic second page. yet I print my variables and they work on the first script and somehow don't on the second. This is my code. in the meantime I will look into cookies Thank you!
Have you tried Cookies
You can always use cookies, but you may run into their limitations. These days, cookies are not the best choice, even though they have the ability to preserve data even longer than the current window session.
or you can make a GET request to the other page by attaching your serialized object to the URL as follows:
http://www.app.com/second.xyz?MyObject=SerializedData
That other page can then easily parse its URL and deserialize data using JavaScript.
you can check this answer for more details Pass javascript object from one page to other

Using Localstorage to store and retrieve javascript variables from one html page to another (DOM)

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();

How to automatically reload a web page

I want my website page to reload once when it has already opened for the first time. I wrote this function in my javascript file for that...
var i;
$(document).ready(function(){
for ( i=0;i<1;i++){
if(i===0){
location.reload();
break;
}
}
});
But the page keeps reloading again and again as if the above function was a recursive one.
How do I do this?
P.S I'm doing it because of this issue.
<script type='text/javascript'>
(function() {
if( window.localStorage ) {
if( !localStorage.getItem('firstLoad') ) {
localStorage['firstLoad'] = true;
window.location.reload();
} else
localStorage.removeItem('firstLoad');
}
})();
</script>
Here is what's happening:
The page loads for the first time, jQuery calls any handlers on the document.ready event
The page reloads
The document.ready call is made again
repeat
Out of curiosity, why would you want to do that? And why do you have a for loop that will run for one iteration?
Also, to answer your question as far as I know the only way to make sure the page doesn't reload is use a cookie that lasts for about 5 seconds. Then, on document.ready check for that cookie and if it exists then don't reload.
You must either set a cookie (or use javascript's localStorage), or use xhr to retrieve a value held on a remote server.
If you want to use cookies, it's as simple as
document.cookie = "username=John Doe";
where the document.cookie is a query string of the form (x=y;a=b;n=z)
If you want the page to reload every time the user vists, be sure to unset the cookie once you've done any necessary processing when a page reload has been set.
$( window ).load(function() {
if (window.location.href.indexOf('reload')==-1) {
window.location.replace(window.location.href+'?reload');
}
});
Code is ok. But if the page is opened from another page with a link to an id (.../page.html#aa) the code only works with firefox. With other browsers reload the page without going to id. (Sorry for my english).
I found the solution with this code. It is assumed that the page is refreshed no earlier than one hour. Otherwise, add minutes to the oggindex variable.
<script>
var pagina = window.location.href;
var d = new Date();
var oggiindex = d.getMonth().toString()+'-'+d.getDate().toString()+'-'+d.getHours().toString();
if (localStorage.ieriindex != oggiindex)
{
localStorage.setItem("ieriindex", oggiindex);
window.location.replace(pagina);
}
</script>
Yours code executed each time $(document).ready(), so it's not surprise that your loop is infinity - each load finished as ready state.
If you give more detailed requirements we can solve it with no using window object as data holder. It's bad way but you can set it for test.
Window object stores variables not depend on reload because it's higher then document.
Let's try:
if( window.firstLoad == undefined ){
// yours code without any loop
// plus:
window.firstLoad = false;
}
You can make it with localStorage API.
Check this link also, it's giving more information about window object variables:
Storing a variable in the JavaScript 'window' object is a proper way to use that object?

How can I get the time a particular window is open?

I have a simple user survey form in which there is one section where the user needs to click on a link, read the page inside the link and then come back to continue the form. Currently, I have a parent HTML page from which I am providing a link to open a child web page in a different window/tab.
How can I obtain the time the user spent on the child window/tab?
listen to the user's click by something like
$('a').on('click', function(){
var d = new Date();
var curr_time = d.getTime();
//save in cookie1
})
and now in the other html page where the user is reading....do the same thing but only on window's unload
$(window).unload(function(){
var d1 = new Date();
var curr_time1 = d1.getTime();
//save in cookie2
})
save this also....
then when s/he comes back I mean on its onfocus you can subtract the values of these 2 cookies and divide by 1000 to get seconds as these time will be in milliseconds.
(cookie1 -cookie2)/1000 seconds //if the cookie thing is used
Does the user leave the page by clicking on the link, or is the second page displayed inside the first one? In the first case, you'll have to use a cookie to store the click time, in the second case, use a variable. Time can be retrieved using new Date().
Record the time of window open
Open the page in a named window
Set a timeinteval function (on original page) to check the location.href of the named window of say 1000 ms
if changed (to a finished/thankyou page) or not existing user must have finished reading
You should set a cookie or an DOM storage value while the page-to-read is open. In that page:
var isFocused = true; // just opened
var secondsLookedupon = 0; // eventually init with a saved value
window.onblur = function(){ isFocused=false; }; // use addEventHandler and co
window.onfocus = function(){ isFocused=true; }; // use addEventHandler and co
window.setInterval(function(){
if (!isFocused) {
secondsLookedupon++;
document.cookie.name = secondsLookedupon; // set a cookie in some way
window.sessionStorage.setItem("name", secondsLookedupon); // or use DOM storage
}
}, 1000);
and from the survey form page you can read that value from the cookie or domstorage whenever you need.

How to delete a localStorage item when the browser window/tab is closed?

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;

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