Button calls ajax function multiple - php

Question

Quick notes. I am not using jQuery so don't suggest it.
When pressing the button which has the onclick="ajaxfunction();" i get an alert saying "Error during AJAX call. Please try again " and then I get the alert saying success, twice :S ... Why is this happening?
I don't understand why this is happening, as it calls the error, and then goes to the other part of the if statement...
Thanks in advance!
<script>
function getXMLObject() //XML OBJECT
{
var xmlHttp = false;
try {
xmlHttp = new ActiveXObject("Msxml2.XMLHTTP") // For Old Microsoft Browsers
}
catch (e) {
try {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP") // For Microsoft IE 6.0+
}
catch (e2) {
xmlHttp = false // No Browser accepts the XMLHTTP Object then false
}
}
if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {
xmlHttp = new XMLHttpRequest(); //For Mozilla, Opera Browsers
}
return xmlHttp; // Mandatory Statement returning the ajax object created
}
var xmlhttp = new getXMLObject(); //xmlhttp holds the ajax object
var url="insertProduct.php";
function ajaxFunction() {
var getdate = new Date(); //Used to prevent caching during ajax call
if(xmlhttp) {
var name = document.getElementById("name");
var code = document.getElementById("code");
xmlhttp.open("POST",url,true); //calling insertProduct.php using POST method
xmlhttp.onreadystatechange = handleServerResponse;
xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
xmlhttp.send("name=" + encodeURIComponent(name.value) + "&code=" + encodeURIComponent(code.value)); //Posting to PHP File
}
}
function handleServerResponse() {
if (xmlhttp.readyState == 4 || xmlhttp.readyState=="complete") {
alert("Success");
document.getElementById("message").innerHTML=xmlhttp.responseText; //Update the HTML Form element
}
else {
alert("Error during AJAX call. Please try again " + xmlhttp.status);
}
}
</script>

Answer 1

After finishing the task you can call return;
Likes below.
function handleServerResponse() {
if (xmlhttp.readyState == 4 || xmlhttp.readyState=="complete") {
alert("Success");
document.getElementById("message").innerHTML=xmlhttp.responseText;
return;
}
else {
alert("Error during AJAX call. Please try again " + xmlhttp.status);
return;
}
}
I hope this will help to you.