This is a duplicate email check question.

function chkValidEmail() {      
    var email = document.touristSurvey.userEmail.value;
    var exptext = /^[A-Za-z0-9_\.\-]+@[A-Za-z0-9\-]+\.[A-Za-z0-9\-]+/;
        if(exptext.test(email)==false){
        //Email format is Alphabet+Number@Alphabet+Number.Not in alphabetic + numeric format         
        alert("The Email format is invalid.");
        return;
        }else{
            chkEmail();
        }
}

function chkEmail(){
    var chk=false;
    if(document.touristSurvey.userEmail.value != ''){
        var userEmail = $("#userEmail").val();
        $.ajax({ 
               url: "emailChk.or", 
               type: "POST",
               data: {"userEmail" : userEmail},
               dataType:"text",
               cache: false,
               success: function(result){
                   if(result!="0") {
                       alert("The email is duplicated.");
                       return;
                   }else{
                       submitOn();
                   }
               }
        });
    }
}

function submitOn(){
    document.getElementById("submit_btn").innerHTML = "On saving... Please wait.";
    document.touristSurvey.submit();
}