我究竟做错了什么？ 没有错误

Question

function showComments(wallID){
    $.ajax({
      url: "misc/showComments.php",
             type: "POST",
      data: { mode: 'ajax', wallID: wallID }, 
      success: function(msg){

      var $msg = $('#showWallCommentsFor'+wallID).find('.userWallComment');
// if it already has a comment, fade it out, add the text, then toggle it back in
if ( $msg.text().length ) {
  $msg.fadeOut('fast', function(){
    $msg.text( msg ).slideToggle(300); 
  });
} else {
  // otherwise just hide it, add the text, and then  toggle it in
  $msg.hide().text( msg ).slideToggle(300); 
}
      }
    });
}

msg, the response i get: ( firebug )

    <span class='userWallComment'>
<span style='float: left;'>
<img style='border: 1px solid #ccc; width: 44px; height: 48px; margin-right: 8px;' src='images/profilePhoto/thumbs/noPhoto_thumb.jpg'>
</span></span>
<span style='font-size: 10px; margin-bottom: 2px;'>
<a href='profil.php?id=1'>Navn navn</a> - igår kl. 01:55
</span>
<br>
DETTE ER EN TEST
<br>
<div class="clearfloat"></div>
</span>

It sends and execute the ajax call properly, and it have something in response, but it doesnt toggle it?

This is the div:

<div id="showWallCommentsFor<?php echo $displayWall["id"]; ?>" style="display: none;">
</div>

Answer 1

The Problem

Your if - else statement has a flaw:

if ( $msg.text().length ) {
  //  ...
} else {
  // $msg has a length of ZERO by definition here!!!
  $msg.hide().text( msg ).slideToggle(300); 
}

The very first time the AJAX call is fired #showWallCommentsFor is empty, so it doesn't have .userWallComment inside it so, $msg will not be defined.

The Solution

You should add text directly to the original div in your else , using:

if ( $msg.text().length ) {
  //  ...
} else {
    // otherwise just hide it, add the text, and then  toggle it in
      // You cannot use $msg here, since it has a length of 0.
      // Add text directly to the original div instead.
      // You do not need to hide the DIV first since it is already 
      // invisible.
    $('#showWallCommentsFor'+wallID).text( msg ).slideToggle(300); 
 }

Finally, in your else , there's no need to .hide() the #showWall... div, since the div is orginally invisible due to style="display: none;" .