Use localStorage to share one comet across multiple tabs

README.md

NOTE:

• The tab which triggers the localStorage's key/value will not fire 'storage' event. But the others will.
• If the tab is exited with an exception, then it won't fire 'storage'.

gistfile1.js

var timeId = (new Date()).getTime();
window.addEventListener('load', function () {
    var tabs = localStorage.getItem('tabs');

    if (!tabs) {
        localStorage.setItem('tabs', JSON.stringify([timeId]));
        localStorage.setItem('comet', timeId);
        console.log('comet connect');
    } else {
        var tabArray = JSON.parse(tabs);
        tabArray.push(timeId);
        localStorage.setItem('tabs', JSON.stringify(tabArray));
    }
});

window.addEventListener('storage', function (e) {
    var key = e.key;

    switch (key) {
        case 'comet':
            // if comet's new value is null,
            // then prepare connect another comet
            if (!e.newValue) {
                var tabs = localStorage.getItem('tabs');
                var tabArray = JSON.parse(tabs);
                if (tabArray[0] === timeId) {
                    console.log('another commet connect');
                    localStorage.setItem('comet', timeId);
                }
            }
            break;
    }
});

window.addEventListener('beforeunload', function (e) {
    var tabs = localStorage.getItem('tabs');
    var comet = localStorage.getItem('comet');
    var tabArray = JSON.parse(tabs);

    if (tabArray.length !== 1) {
        tabArray = tabArray.filter(function (item) {
            return item !== timeId;
        });
        localStorage.setItem('tabs', JSON.stringify(tabArray));
    } else {
        localStorage.removeItem('tabs');
    }
    
    // if this comet tab is closed, then remove 'comet' key in localStorage
    if (comet == timeId) {
        localStorage.removeItem('comet');
        console.log('comet disconnect');
    }
});

cool!