JSFiddle - React, Tailwind, and code Playground

HTML

See <a href="http://stackoverflow.com/a/10505907/938089?is-there-any-workaround-to-make-use-of-html5-localstorage-on-both-http-and-https">Stack Overflow answer</a>

JavaScript

// Script at https://my.domain.org/postMessage
window.addEventListener('message', function(event) {
    console.log('Receiver debugging', event);
    if (event.origin != 'justademo') {
        var data = JSON.parse(event.data);
        if ('setItem' in data) {
            localStorage.setItem(data.setItem, data.value);
        } else if ('getItem' in data) {
            var gotItem = localStorage.getItem(data.getItem);
            // See below
            event.source.postMessage(
                '#localStorage#' + data.identifier + 
                (gotItem === null ? 'null#' : '#' + gotItem),
                event.origin
            );
        } else if ('removeItem' in data) {
            localStorage.removeItem(data.removeItem);
        }
    }
}, false);