user/public/js/shared-worker.js

const clients = [];

self.onconnect = function(e) {
    console.log(1)
    const port = e.ports[0];
    clients.push(port)

    port.onmessage = function(e) {
        const message = e.data;

        clients.forEach(client => client.postMessage(message))
    }

    port.isMaster = function() {
        clients.forEach(client => client.postMessage({tabId: port.tabId}))
    }

    port.setMaster = function(tabId) {
        port.tabId = tabId;
    }
}