Why isn't this textarea focusing with .focus()?

Question

I have this code to focus a textarea when the user clicks on the "Reply" button:

$('#reply_msg').live('mousedown', function() {
    $(this).hide();
    $('#reply_holder').show();
    $('#reply_message').focus();
});

It shows the reply form, but the textarea won't focus. I'm adding the textarea via AJAX which is why I am using .live(). The box that I add shows (I even add #reply_msg via AJAX and stuff happens when I mouse down on it) but it won't focus on the textarea.

---

Edit

My HTML looks like:

<div id="reply_msg">
  <div class="replybox">
  <span>Click here to <span class="link">Reply</span></span>
  </div>
  </div>
  <div id="reply_holder" style="display: none;">
  <div id="reply_tab"><img src="images/blank.gif" /> Reply</div>
  <label class="label" for="reply_subject" style="padding-top: 7px; width: 64px; color: #999; font-weight: bold; font-size: 13px;">Subject</label>
  <input type="text" id="reply_subject" class="input" style="width: 799px;" value="Re: <?php echo $info['subject']; ?>" />
  <br /><br />
  <textarea name="reply" id="reply_message" class="input" spellcheck="false"></textarea>
  <br />
  <div id="reply_buttons">
  <button type="button" class="button" id="send_reply">Send</button>
  <button type="button" class="button" id="cancel_reply_msg">Cancel</button>
  <!--<button type="button" class="button" id="save_draft_reply">Save Draft</button>-->
  </div>
</div> 

Answer 1

A mouse-click on a focusable element raises events in the following order:

1. mousedown
2. focus
3. mouseup
4. click

So, here's what's happening:

1. mousedown is raised by <a>
2. your event handler attempts to focus the <textarea>
3. the default event behavior of mousedown tries to focus <a> (which takes focus from the <textarea>)

Here's a demo illustrating this behavior:

$("a,textarea").on("mousedown mouseup click focus blur", function(e) {
  console.log("%s: %s", this.tagName, e.type);
})
$("a").mousedown(function(e) {
  $("textarea").focus();
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<a href="javascript:void(0)">reply</a>
<textarea></textarea>

So, how do we get around this?

Use event.preventDefault() to suppress mousedown's default behavior:

$(document).on("mousedown", "#reply_msg", function(e) {
    e.preventDefault();
    $(this).hide();
    $("#reply_message").show().focus();
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<a href="javascript:void(0)" id="reply_msg">reply</a>
<textarea id="reply_message"></textarea>