detect inactive tabs with js

inactivity.js

//handles tab inactivity
var vis = (function() {
    var stateKey, eventKey, keys = {
        hidden: "visibilitychange",
        webkitHidden: "webkitvisibilitychange",
        mozHidden: "mozvisibilitychange",
        msHidden: "msvisibilitychange"
    };
    for (stateKey in keys) {
        if (stateKey in document) {
            eventKey = keys[stateKey];
            break;
        }
    }
    return function(c) {
        if (c) document.addEventListener(eventKey, c);
        return !document[stateKey];
    }
})();


//call the function, use same function as param for verification:
vis(function() {
    if (vis()) {
        console.log('focus!')
        var id = window.setTimeout(function() {}, 0);
        while (id--) {
            window.clearTimeout(id); // will do nothing if no timeout with id is present
        }
        jQuery('.messages ul li').removeClass('active')
        videoElement.load()
    }
})