I want to run Javascript countup timetracker in the background when page closed

I want run the javascript countup timetracker in the background when page closed

$(document).ready(function(){

t.run = function() {
    $( "#table input[type=checkbox]" ).each(function(index){
        var tr = $(this).closest('tr');

        if ($(this).is(":checked")) {   
            var total = tr.find('.total'),
                rate = tr.find('.rate'),
                timed = tr.find('.timed');

            total.data('value', total.data('value') + (rate.val()/3600) );
            total.val( t.config.currency+total.data('value').toFixed(2) );
            timed.data('value', parseInt(timed.data('value')) + 1 );
            timed.val( t.niceTime(timed.data('value')) );

            tr.addClass('success');
        }else{
            tr.removeClass('success');
        }
    });

    // Update title and save countdown
    if ($('.timer:checked').length>0) {
        document.title = '('+$('.timer:checked').length+') Timetracker';
        t.config.savenext = t.config.savenext - 1000;
    }else{
        document.title = 'Timetracker';
    }
    // Saving time?
    if (t.config.savenext <= 0) {
        t.config.savenext = t.config.savedefault;
        t.save();
    }

};

t.save = function() {

    var data = {};

    $( "#table tr.taskrow" ).each(function(index){
        var tr = $(this);
        var row = {
            timer: tr.find('.timer').checked,
            date: tr.find('.date').val(),
            client: tr.find('.client').val(),
            task: tr.find('.task').val(),
            rate: tr.find('.rate').val(),
            total: tr.find('.total').data('value'),
            desc: tr.find('.desc').val(),
            timed: tr.find('.timed').data('value')
        };

        data[tr.data('id')] = row;
    });


    var jsondata = JSON.stringify(data);

    $.ajax({
        type: "POST",
        url: "?action=save",
        data: { json: jsondata }
    })
    .done(function( msg ) {
        console.log(msg);
    });

};

t.load = function() {
    jsondata = t.config.initialdata;
    data = JSON.parse(jsondata);

    $('#table tbody').html('');
    var buffer = '<!--start-->';
    //console.log(data);
    for (var key in data) {
        var obj = data[key];
        buffer += 
            '<tr id="task-'+key+'" data-id="'+key+'" class="taskrow">' +
                '<td><input class="timer" type="checkbox" class="save-cb-state" id="timetrackercheckbox" name="timetrackercheckbox" value="yes"></td>' +
                '<td><input class="task input-large" type="text" placeholder="Case" value=""></td>' +
                '<td><input class="date input-mini" type="text" placeholder="Date" value="'+obj.date+'"></td>' +
                '<td><input class="client input-mini" type="text" placeholder="Client" value="'+obj.client+'" style="color:'+t.generateColor( obj.client )+'"></td>' +
                '<td><input class="task input-large" type="text" placeholder="Task" value="'+obj.task+'"></td>' +
                '<td><input class="rate input-mini" type="text" placeholder="'+obj.rate+'" value="'+obj.rate+'"></td>' +
                '<td><input class="total input-mini" data-value="'+obj.total+'" type="text" placeholder="'+t.config.currency+obj.total.toFixed(2)+'" value="'+t.config.currency+obj.total.toFixed(2)+'"></td>' +
                '<td><input class="desc" type="text" placeholder="Notes" value="'+obj.desc+'"></td>' +
                '<td><input class="timed input-mini" type="text" placeholder="0:00:00" data-value="'+obj.timed+'" value="'+t.niceTime(obj.timed)+'"></td>' +
                '<td><button class="delete btn btn-danger btn-small" title="Clear task"><i class="icon-remove icon-white"></i></button></td>' +
            '</tr>';
    };
    //console.log(buffer);
    $('#table tbody').html(buffer);

};

t.niceTime = function(s) {
    if (!s) {s=0;}
    hours = parseInt( s / 3600 ) % 24;
    minutes = parseInt( s / 60 ) % 60;
    seconds = s % 60;

    return (hours < 10 ? "0" + hours : hours) + ":" + (minutes < 10 ? "0" + minutes : minutes) + ":" + (seconds  < 10 ? "0" + seconds.toFixed(0) : seconds.toFixed(0));
};

t.generateColor = function(string) {
    string += 'makeitlongerjustincase';
    var hash = '',
        curchar;
    for (var i = 0; i < string.length; i++) {
        curchar = (string.toLowerCase().charCodeAt(i)-97) /25*255;
        curchar = parseInt(curchar.toFixed(0), 10).toString(16);
        hash += curchar;
    }
    return '#'+hash.substr(0,6);
};


/**
 * Events
 */

$('#save').on('click', function() {
    t.config.savenext = 0;
});

$('button.delete').live('click', function() {
    if (confirm('Are you sure you want to delete this task?')) {
        var tr = $(this).closest('tr');
        tr.find('.task').val('');
        tr.find('.client').val('');
        tr.find('.total').data('value', 0);
        tr.find('.total').val(t.config.currency+'0.00');
        tr.find('.rate').val(t.config.rate);
        tr.find('.desc').val('');
        tr.find('.timed').data('value', 0);
        tr.find('.timed').val('00:00:00');
    }
    t.config.savenext = 0;
});

// Update time manually
$(document.body).on('keyup', 'input.timed', function() {
    var secs = $(this).val().split(':');
    $(this).data('value', parseInt(secs[0])*3600+parseInt(secs[1])*60+parseInt(secs[2]));
    t.config.savenext = 0;
});

// Update total manually
$(document.body).on('keyup', 'input.total', function() {
    $(this).data('value', parseFloat($(this).val().replace(/[^0-9\.]/g, '')) );
    t.config.savenext = 0;
});

// Change color of Client
$(document.body).on('input paste', 'input.client', function() {
    $(this).css('color', t.generateColor( $(this).val() ) );
    t.config.savenext = 0;
});

// Trigger saving when editing other fields too
$(document.body).on('keyup', 'input.date,input.task,input.rate,input.desc', function() {
    t.config.savenext = 0;
});

setInterval(function(){t.run();}, 1000);

t.load();

});