Increment number counter animation

incrementNumber = function($block, start, finish, duration) {
    if (typeof(start)=='undefined') {
        var start = 0;
        if ($block.text().trim()*1)
            start = $block.text().trim()*1;
    }
    for (var i=0; i<=duration/100; i++) {
        var nb = Math.round(finish/((duration/100)/i));
        setTimeout(function(nb) {
            $block.html(nb);
        }.bind(null,nb),i*100);
    }
}