XTab

XTab is a small utility library that provides an easy API for communicating between tabs and for automatically electing a primary (or "master") tab.

Having a primary tab is useful when you want to maintain a single (or at least one) websocket or push connection for your web app.

For security purposes, the browser restricts cross-tab communication to tabs under the same domain.

API

Initializing

In each tab, you need to instantiate the XTab class and then call start:

const xtab = new XTab();
xtab.start();

Broadcasting

To send an event to all tabs, use the broadcast method:

xtab.broadcast('myEvent',  {foo: 'bar'});

Listening

To listen for events from other tabs, you can call once for a one-time listener, and on to listen indefinitely.

xtab.once('myEvent',  data => alert(data.foo));
xtab.on('myEvent',  data => console.log(data.foo));

Events

Once a tab is designated to be the master tab, the isMaster event will be triggered.

xtab.on('isMaster',  data => {
    if (data.value) {
        alert(`The tab with id ${data.xtabid} is now the master tab`);
    } else {
        alert(`The tab with id ${data.xtabid} is no longer the master tab`);
    }
});

Properties

The xtab instance will have certain properties that you can read.

if (xtab.isMaster) {
    // this is the master tab
}

if (xtab.isFocused) {
    // this tab is focused
}

Credits

XTab is inspired by the WindowController class, by Fastmail Pty Ltd.