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javascript - LocalStorage returning null in a different tab in chrome

This is my issue:

I update the localStorage in popup.js in a new tab. I access the same localStorage(same key) in the background.js.

Now this is returning null in every tab apart from the chrome://extensions tab(when I load the extensions.)

I thought localStorage was persistant across all tabs.

Code:

popup.js:

$(document).ready(function (){

    alert(localStorage.getItem('filters'));
    var oldFilters = localStorage.getItem('filters');
    //All the filters show up on the popup.html page.
    document.getElementById('td1').innerHTML = oldFilters;

    var dat = oldFilters + "," + newArray[j]
    localStorage.setItem('filters',String(dat));
}

background.js:

$(window).ready(function() {
  // Handler for .ready() called.

 var filters = localStorage.getItem('filters');

   alert("background + "+ filters);
    //This shows all the filters in the chrome:extensions page but always pops up "background + null" in every new tab load. 

//changeImage(filters);

});
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1 Answer

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by (71.8m points)

Background and Browser Action(In your case) Pages live in isolated worlds, their local storage details are not accessible to each other, if you want this sort of access to happen use chrome.storage for your storage needs.

It has few advantages

  • Your extension's content scripts can directly access user data without the need for a background page.
  • A user's extension settings can be persisted even when using split incognito behavior.
  • User data can be stored as objects (the localStorage API stores data in strings).

Methods used

Demonstration

manifest.json

Ensure all permissions are available for accessing storage API.

{
"name":"Local Storage Demo",
"description":"This is a small use case for using local storage",
"version":"1",
"manifest_version":2,
"background":{
    "scripts":["background.js"]
},
"browser_action":{
    "default_popup":"popup.html",
    "default_icon":"logo.png"
},
"permissions":["storage"]
}

popup.html

A trivial popup html page which refers popup.js to surpass CSP.

<!doctype html>
<html>
<head>
<script src="popup.js"></script>
</head>
<body>
</body>
</html>

background.js

This scripts sets content to chrome storage

//Set some content from background page
chrome.storage.local.set({"identifier":"Some awesome Content"},function (){
    console.log("Storage Succesful");
});
//get all contents of chrome storage
chrome.storage.local.get(null,function (obj){
        console.log(JSON.stringify(obj));
});

popup.js

This script retrieves and sets content fromo chrome storage

document.addEventListener("DOMContentLoaded",function (){
    //Fetch all contents
    chrome.storage.local.get(null,function (obj){
        console.log(JSON.stringify(obj));
    });
    //Set some content from browser action
    chrome.storage.local.set({"anotherIdentifier":"Another awesome Content"},function (){
        console.log("Storage Succesful");
    });
});

If you look at outputs of these js pages, communication of storage (Background -> popup and popup -> background) is achieved.


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