如何在按键的同时停止通过aJax重新发送脚本？

Question

I have a script which stores message into DB when enter key is pressed.

<textarea class="comment" name="comment" id="comment" onKeyPress="return checkSubmit(event)" onKeyDown="return checkTypingStatus(event)" >Comment/Reply</textarea>

function checkSubmit(e)
    {

       if(e && e.keyCode === 13)
       {

                var sender = <?=$_REQUEST['sender'];?>;
                var user_id = <?=$_SESSION['userid'];?>;
                var cid = <?=$_REQUEST['cid'];?>;

                var comment = $("#comment").val();

                comment = encodeURIComponent(comment);

                var dataString = 'sender='+ sender + '&user_id=' + user_id + '&comment=' + comment + '&cid=' + cid;

                        if(comment=='' || comment=='Comment%2FReply')
                         {
                            alert('Please Give some text into message box.');
                         }
                    else
                        {
                        $("#flash").show();
                        $("#flash").fadeIn(400).html('<img src="images/ajax-loading.gif" align="absmiddle">&nbsp;<span class="loading">Sending Message...</span>');
                    $.ajax({
                                type: "POST",
                                url: "ajax_comment.php",
                                data: dataString,
                                cache: false,
                                success: function(html){

                                        $("p#update").append(html);
                                        $("p#update").fadeIn("slow");
                                        document.getElementById('comment').value='';
                                        $("#comment").focus();


                                        $("#flash").hide();
                                }
                            });
                        }       
                        return false;

       }
    }

Everything is working okay except if user keeps pressing enter key for long time the same message is stored multiple times until the enter is released.

I have tried the same script with onKeyUp event. But the script does not work as it should be.

Answer 1

Just put a lock to disable the ajax request until the last one has finished:

var lock = false;
function checkSubmit(e)
    {

       if(e && e.keyCode === 13 && !lock)
       {
        lock = true;
        ....
        $.ajax({
        ....
        success: function(html){
             lock = false;
        ...

Another option could be disabling the textarea and checking if it's disabled or not instead of using the lock but I think you got the idea with this example.