Cross Domain Cookie/LocalStorage Sharing using JavaScript

This will help to cross domain sharing resources like login cookies data or local storage data between two subdomain or domain.

Installation

Not required

Usage

Just fork code or copy reference code block and use in your html or Javascript files.

Consider we have two domain example.com and example2.com.

Step1 : Add postCrossDomainMessage function in landing page like index.html www.example.com/index.html

function postCrossDomainMessage(msg) {
  var win = document.getElementById('ifr').contentWindow;
  win.postMessage(msg, "http://example.com/");
}
var postMsg = {"login": "user"}; // this is just example
postCrossDomainMessage(postMsg);

Step2: Add iframe tag in landing page where everywhere reflected. For Angular/React you can add it in index.html

<iframe style="display:none;" src="http://example.com/getlocalstorage.html" id="ifr"></iframe>

Step3: On recipient domain www.example2.com create getlocalstorage.html file and put this code 👇🏻 in file getlocalstorage.html

var PERMITTED_DOMAIN = "http://example.com";
/**
 * Receiving message from other domain
 */
window.addEventListener('message', function(event) {
    if (event.origin === PERMITTED_DOMAIN) {
        //var msg = JSON.parse(event.data);
        // var msgKey = Object.keys(msg)[0];
        if (event.data) {
            localStorage.setItem("localstorage", event.data);
        } else {
            localStorage.removeItem("localstorage");
        }
    }

});