Question

I have an Ajax call written in prototype and need to convert it to jquery. I’m not well versed in requestHeaders and the like, so I’m a bit stumped. Here’s the prototype version:

function poll_for_update(feed_id, last_modified, link) {
  setTimeout(function() {
    new Ajax.Request('/feeds/' + feed_id, {
      method: 'get',
      requestHeaders: { 'If-Modified-Since': last_modified },
      onComplete: function(transport) {
        if (transport.status == 304) {
          poll_for_update(feed_id, last_modified, link);
        } else if (transport.status == 200) {
          $('feed_' + feed_id).innerHTML = transport.responseText
        } else {
          link.innerHTML = 'error'
        }
      }
    }) },
    1000
  )
}

Since I can extract the feed_id and last_modified dates from the link, my early version of the corresponding jquery functions looks like this:

function poll_for_update(link) {
    var feed_id = $(link).attr('feed_id')
    var last_modified = $(link).attr('last_modified')
    setTimeout(function() {
        $.ajax({
            url: show_path(link),
            type: 'get',
            ifModified: true,
            headers: { 'If-Modified-Since': last_modified },
            statusCode: {
                404: function() {
                    alert('404');
                },
                304: function() {
                    alert('304');
                },
                200: function() {
                    alert('200');
                }
            },
            success: function( data ) {
                alert('success');
            },
            complete: function() {
                alert('complete');
            }});
    }, 1000)
}

A few things I can’t figure out:

• how do I extract transport.status from within the complete() function?
• do I need the statusCode: clause, or is the complete: clause sufficient?
• is the ifModified clause necessary?

… etc.

(For the curious, this is a transcription of Adam Wiggins’s tutorial on how to build a queue-backed feed reader, which is super useful but somewhat outdated.)

TIA.

Answer 1

Here’s what I ended up with, and it appears to work. What wasn’t obvious to me was that the ‘transport’ object is passed as an argument to the completion() method. Once I realized that, the jquery implementation is quite close to the prototype version:

function poll_for_update(link) {
    var feed_id = $(link).attr('feed_id')
    var last_modified = $(link).attr('last_modified')
    setTimeout(function() {
        $.ajax({
            url: show_path(link),
            type: 'get',
            headers: { 'If-Modified-Since': last_modified },
            complete: function( transport ) {
                if (transport.status == 304) {
                    poll_for_update(link)
                } else if (transport.status == 200) {
                    $('#feed_' + feed_id).html(transport.responseText)
                } else {
                    $(link).html('error ' + transport.status)
                }
            }
        });
    }, 1000)
}