ajax调用后文本框不清除

I have this chat room on my website, where the user types their message into a textbox and when they press enter (or the send button), jQuery takes the data from the textbox, disables the textbox, sends the data to the file send.php where it is then processed and put into the database, and then it should clear and undisable the textbox once it successfully runs through the PHP script. What is happening is the data is being submitted and it runs through the script (sends the data to the database successfully) but the jQuery is not clearing and undisabling the textbox. Can someone explain to me what is wrong?

jQuery:

$('#formSend').on('submit', function (e) {

    e.preventDefault();

    var textArea = document.getElementById('styled');

    if( textArea.value != "" ) {

        var formData = $('form').serialize();
        $('.expand').prop("disabled", true)

        $.ajax({
            type: 'post',
            url: 'send.php',
            data: formData,
            dataType: "json",
            success: function (formData) { //put data in parentheses when coming back
                alert("Success");
                $(".expand").val('');
                $('.expand').prop("disabled", false);

                if( formData["banned"] == 1 ) {
                    var rel = confirm("You have been banned.");
                    if (rel) {
                        location.reload();
                    }
                    else {
                        location.reload();
                    }
                }
            }
        });
    }
    else {
        alert("Your message must be longer than 1 (one) character.");
        $('#styled').focus();
    }
});

send.php:

<?php

include("../config.php");
session_start();


$msg           = strip_tags( $_POST['msg'], '<b></b>' );

if( $msg == "" ) {
 exit("There is no message.");
}
$username      = $_SESSION['USER'];
$date          = new DateTime();
$formattedDate = $date->format('Y-m-d H:i:s');

$stmt = $db->prepare("SELECT id, username FROM users WHERE username = :username");

$stmt->execute(array(":username" => $username));

$row = $stmt->fetch();

$userID = $row['id'];

$checkBanned = $db->prepare('SELECT banned FROM users WHERE username = :username');
$checkBanned->execute(array(
            ':username' => $username
        ));
$banned = $checkBanned->fetch();

if( $banned['banned'] == "yes" ) {
    $return = array('banned' => 1);
    echo json_encode($return);
    exit;
}

try {

    $stmt = $db->prepare('INSERT INTO `chat-messages` (userID,msg,date) VALUES (:userID, :msg, :date)');
    $stmt->execute(array(
        ':userID' => $userID,
        ':msg' => $msg,
        ':date' => $formattedDate
    ));
}
catch(PDOException $e) {
    echo $e->getMessage();
}
?>

Here is the form too, if needed.

<form action="send.php" method="post" name="formSend" id="formSend" />
     <textarea id="styled" class="expand" name="msg" placeholder="Your Message Here" onfocus:"setbg(\'#e5fff3\');"required></textarea>
     <input type="hidden" name="banned" value="no" />
     <input type="submit" name="submit" value="Send" class="send" />

  </form>

Have you tried something like:

$('.expand').removeAttr("disabled");

I see you are refreshing the page afterwards, that could make the form to autocomplete to the previous value, try this:

  <form autocomplete="off" action="send.php" method="post" name="formSend" id="formSend" />
     <textarea id="styled" class="expand" name="msg" placeholder="Your Message Here" onfocus:"setbg(\'#e5fff3\');"required></textarea>
     <input type="hidden" name="banned" value="no" />
     <input type="submit" name="submit" value="Send" class="send" />
  </form>

I think the problem is you have not sent any responce if user is not banned and message is stored successfully.

If "success" is not being alerted then that is the problem.

Try this,

try { $stmt = $db->prepare('INSERT INTO `chat-messages` (userID,msg,date) VALUES (:userID, :msg, :date)'); $stmt->execute(array( ':userID' => $userID, ':msg' => $msg, ':date' => $formattedDate ));
$output = "success";
 } catch(PDOException $e) { $output =  $e->getMessage(); } 
finally{
echo  json_encode($output);
}

If you dont want to reload the page (which should actually happen, if you dont prevent the submit event from beeing triggered in the ajax callback by event.preventDefault()) you have to reset the form by doing something like $('#formSend').reset();

Furthermore, there is no disabled='false', you need to remove the attribute: $('.expand').removeAttr('disabled');.

By the way, it is good habit to save selector you need more than one time ;)