Jquery to detect particular div(id) OR div(class) appears or not

// function to detect passed element is appear or not

$.fn.isOnScreen = function(){
        var win = $(window);
        var viewport = {
            top : win.scrollTop(),
            left : win.scrollLeft()
        };
        viewport.right = viewport.left + win.width();
        viewport.bottom = viewport.top + win.height();
        var bounds = this.offset();
        bounds.right = bounds.left + this.outerWidth();
        bounds.bottom = bounds.top + this.outerHeight();
        return (!(viewport.right < bounds.left || viewport.left > bounds.right || viewport.bottom < bounds.top || viewport.top > bounds.bottom));
        };

// Just replace this line with your id, tag, class      

    var isthere = $('#yourid').isOnScreen();
    if(isthere == true)
    {
          // Do something for appear
    }
   else
    {
       // Do something not appear
    }