สอบถามการใช้ ajax ตรวจ username ว่ามีในระบบแล้วครับ

function validateUsername(){
		if(username.val() == ""){
			username.addClass("error");
			                         usernameDetail.html("<< กรุณากรอกข้อมูล");
			usernameDetail.addClass("error");
			return false;
		}else if(username.val().length < 6){
			username.addClass("error");
			                         usernameDetail.html("<< น้อยกว่า 4 ตัวอักษร");
			usernameDetail.addClass("error");
		}else{
			username.removeClass("error");
			usernameDetail.html('<img src="images/icon-yes.png" align="absmiddle">');
			usernameDetail.removeClass("error");
			return true;
		}
	}

if(username.length > 5){
$("#usernameDetail").html('<img src="images/icon-loader.gif" align="absmiddle">');

$.ajax({  
    type: "POST",  
    url: "usernamecheck.php",  
    data: "username="+ username,  
    success: function(msg){  
   $("#usernameDetail").ajaxComplete(function(event, request){ 
    if(msg == 'OK'){ 
		$("#username").addClass("error");
        usernameDetail.html('<img src="images/icon-yes.png" align="absmiddle">');
		$("#username").removeClass("error");
    }else{  
		$("#username").removeClass("error");
		$("#username").addClass("error");
        usernameDetail.html(msg);
	}