尝试使用ajax检查实时电子邮件可用性

Question

function checkAvailability() {
    $("#loaderIcon").show();
    jQuery.ajax({
        url: "check_availability.php",
        data:'email='+$("#email").val(),
        type: "POST",
        success:function(data){
            $("#user-availability-status").html(data);
            $("#loaderIcon").hide();
        },
        error:function (){}
    });
}

代码工作正常....... 但是如果电子邮件已经存在于数据库中，那么表单不应该提交 ...我刚接触java脚本该怎么办？

<?php
include('conection.php');


if(!empty($_POST["email"])) {
  $result = mysql_query("SELECT * FROM user WHERE email='" . $_POST["email"]
        . "'");
 $row = mysql_fetch_row($result);
    $user_count = $row[0];
  if($user_count>0) {
  echo "<span class='status-not-available'> Email Already 
    Registered</span>";
  }else{
  echo "<span class='status-available'> Email Available.</span>";
   }
  }
  ?>