Ajax requests to load content while scrolling page

Question

I have tried and searched but didn't find... How can I change the following method that I wrote to work with the on() method?

//Get old posts when scrolling down
$(window).scroll(function(){
  if($(window).scrollTop()==($(document).height()-$(window).height())){
    //Get older posts
    $.ajax({
        type: 'POST',
        url: 'action/getoldposts.php',
        success: function(oldposts){
            //Append #postsDiv
            $('#postsDiv').append(oldposts);
        }
    });
  } 
});

Thanks in advance!

Dennis

UPDATE 1

I changed the code to the following, but then things that are created on the fly don't have functionality - am I missing some static reference?

$(window).on('scroll',function(){
  if($(window).scrollTop()==($(document).height()-$(window).height())){
    //Get older posts
    $.ajax({
        type: 'POST',
        url: 'action/getoldposts.php',
        success: function(oldposts){
            //Append #postsDiv
            $('#postsDiv').append(oldposts);
        }
    });
  } 
});

UPDATE 2

On the fly created elements miss the following functionality:

$('#postsDiv').on('keydown', '.commenttext', function(e) {
    if ((e.which == 13) && !e.shiftKey) {
        comment($(this));
        return false;
    }
});

The method comment() looks as follows:

//Function to comment on a post
function comment(commenttext)
{
//Get postid
var commenttextid=commenttext.attr('id');
var postid=commenttextid.replace("commenttext", "");

//Get commenttext
var commenttext=$('#commenttext'+postid).val();

//Ajax of commenttext is not empty
if(commenttext!="")
{
    $.ajax({
        type: 'POST',
        url: 'action/comment.php',
        data: 'commenttext='+commenttext+'&postid='+postid,
        success: function(data){

            //Prepend comments
            $('#comments'+postid).hide().prepend(
                '<div class="comment"><hr/>'+commenttext.replace( /\n/g, '<br/>' )+'</div'
            ).fadeIn('slow');

            //Remove from textarea what was typed in
            $('#commenttext'+postid).val('');

            //Focus on textarea
            $('#commenttext'+postid).focus();
        }
    }).error(function(){
        alert('The comment could not be sent - please try again later.');
    });
}
else
{
    //If the commenttext is empty, focus on the textarea nonetheless
    $('#commenttext'+postid).focus();
}
}

The comment gets appended to the newly loaded content but apparently missed the ajax as when I reload the page it is not there anymore.

Answer 1

$(window).on('scroll', function(){ 
// ...
});

Answer 2

1) I've made a similar piece of code a few days ago. Here I assign the page scrolling event to a function which checks how much pixels the user is away from the bottom. If the user has 300 or less pixels less the loadMoreArticles() function is triggered:

$(document).scroll(function(){
        if(($(document).height()-$(window).height()-$(document).scrollTop()) < 300){
            console.log('Scrolled to bottom');
            ArticleList.loadMoreArticles();
        } else {
            console.log('Scroll '+$(document).height()+' - '+$(window).height()+' - ' +$(document).scrollTop());
        }
    });

The console.log() functions shows you it's implemented in the right way

2) You can add the functionalities again after you've appended the new content. Like this:

$(window).on('scroll',function(){
  if($(window).scrollTop()==($(document).height()-$(window).height())){
    //Get older posts
    $.ajax({
        type: 'POST',
        url: 'action/getoldposts.php',
        success: function(oldposts){
            //Append #postsDiv
            $('#postsDiv').append(oldposts);
            //Remove all functionalities
            $('#postsDiv').off('keydown');
            //Add all functionalities again
            $('#postsDiv').on('keydown', '.commenttext', function(e) {
                if ((e.which == 13) && !e.shiftKey) {
                    comment($(this));
                    return false;
                }
            });
        }
    });
  } 
});