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Shortening Ajax Code

I am creating fully Ajax based website so all actions calls a different JS function therefore I am using this Ajax Code in each of my function which makes my functions a big code.
if (window.XMLHttpRequest) {
// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else {
// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState==4 && xmlhttp.status==200) {
var getData=xmlhttp.responseText;
if(getData=="something") {
/*
code goes here
*/
}
else {
/*
code goes here
*/
}
}
}
xmlhttp.open("GET","mypage.php",true);
xmlhttp.send();
So I wanted to ask should I use a different function that contains only above Ajax Code and declare my variable getData globally so whenever I need it I should call it.
Here is how I wanted to use
var getData=""; /*declaring var Globally (I read it like this dont know right)*/
function oneAjax(checkPage) {
if (window.XMLHttpRequest) {
// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else {
// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState==4 && xmlhttp.status==200) {
getData=xmlhttp.responseText;
/*now check further in the function which called it*/
}
}
xmlhttp.open("GET",checkPage+".php",true);
xmlhttp.send();
}
Will it create any conflict with other running actions?
or provide me any right solution for my problem.

If you're not going to use an off-the-shelf library, you should pass a "callback" to oneAjax:
function oneAjax(checkPage, done, fail) {
...
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4) {
if (xmlhttp.status == 200) {
done(xmlhttp.responseText, xmlhttp.status);
} else {
fail(xmlhttp.status);
}
}
};
}
Adjust the parameters passed to the callbacks to suit your requirements.
To use:
oneAjax('mypage', function(text, status) {
// success
console.log(status);
}, function(status) {
// failure
console.log(status);
});

why don't you use Jquery or something like this? Such library will much shorten your statements and this will be much easier to write.
But still if you want to do it by your own you should read about javascript promises. On msdn there is a nice tutorial how to solve your problem: Asynchronous Programming in JavaScript with “Promises”

I think using the jQuery library would be better and provide a better low level abstraction
<!-- add a protocol if on local ex: http: -->
<script src="//code.jquery.com/jquery-1.10.0.min.js"></script>
$.ajax({
type: "POST",
url: "some.php",
data: { name: "John", location: "Boston" }
}).done(function( msg ) {
alert( "Data Saved: " + msg );
});
It also offers features like JSONP to get around cross domain issues

What causes error in IE7?

I am using this JS code to reach a list of cities. It works in fireworks, chrome .e.t.c. But in ie7 it does not. the line document.getElementById(oDiv).innerHTML=xmlhttp.responseText; causes the error.
When I change "responseText" to "readyState", "statusText", "readyState" the scripts works. Only "responseText" causes problem.
What is the problem here?
function showAjax(oDiv, countrycode, dowhat) {
if (oDiv == "") {
document.getElementById(oDiv).innerHTML = "";
return;
}
if (window.XMLHttpRequest) { // code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp = new XMLHttpRequest();
} else { // code for IE6, IE5
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.open('POST', 'ajax.php?dowhat=' + dowhat + '&countrycode=' + countrycode, true);
xmlhttp.onreadystatechange = function () {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
document.getElementById(oDiv).innerHTML = xmlhttp.responseText;
//document.getElementById(oDiv).innerHTML=xmlhttp.readyState;
}
}
xmlhttp.send();
}
Click
<div id=citytd></div>

IE7 (and before, and IE8 in "compatibility" mode) has issues with getElementById, where it considers some things IDs that it shouldn't. I suspect you have a global variable, or another element with name="citytd", and IE is pick that up instead (even though, again, it shouldn't). More: ...by any other name, would smell as sweet

ajax internet explorer onchange

My ajax script for loading the second select box, works in firefox and chrome, but internt explorers cant handle it. I call the onChange function from my select box and give the value from the select box to the function.
Code:
function getXMLHTTP()
{
var xmlhttp;
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
return xmlhttp;
}
function getType(categoryName)
{
var strURL="includes/get.php?c="+categoryName+"&sid="+Math.random();
var req = getXMLHTTP();
if (req) {
req.onreadystatechange = function() {
if (req.readyState == 4) {
// only if "OK"
if (req.status == 200)
{document.getElementById('type').innerHTML=req.responseText;
} else {
alert("There was a problem while using XMLHTTP:\n" + req.statusText);
}
}
}
req.open("GET", strURL, true);
req.send(null);
}
}
My second question is, is it possible to send the text between the options tag instead of the value in the options tag?

For your 1st question, I assume your if (req) returns false. Which IE version are you using? Try to add debug codes in getXMLHTTP() function to start diagnosing the codes. Try this solution provided by Microsoft: http://msdn.microsoft.com/en-us/library/ms537505(v=vs.85).aspx
I try not to repeat other's answer. Here is the answer for obtaining text in selected option tag : Getting the text from a drop-down box

AJAX: How to use TWO xmlHttpRequest in parallel in ONE function?

How should I do this?
function(id,id2){
if (window.XMLHttpRequest) { // code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
} else { // code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
First Request:
xmlhttp.open("GET", "http://example.com/ajax.php?id="+id, true);
xmlhttp.send();
Second Request:
xmlhttp.open("GET", "http://example.com/ajax2.php?id2="+id2, true);
xmlhttp.send();
}
Because in this way doesn't works.
I want to make it in plain javascript, so please do not post answers with jQuery or any library etc.
Thanks

It should work if you create a new xmlhttp object. Currently you are attempting to reuse the same object, which is already performing a query so it will not work.

if you are looking for classic javascript style you can use as the following. But use jQuery as it's simple and comprehensive. The one thing to be noted is that the "xmlhr" should be in method (callAjax) scope.
function callAjax(url) {
var xmlhr;
if (window.XMLHttpRequest) {
xmlhr = new XMLHttpRequest();
} else {
xmlhr = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhr.onreadystatechange = function () {
if (xmlhr.readyState == 4 && xmlhr.status == 200) {
alert(xmlhr.responseText);
}
}
xmlhr.open("GET", url, true);
xmlhr.send();
}
function myFunction(id1, id2) {
callAjax("http://example.com/ajax2.php?id2=" + id1);
callAjax("http://example.com/ajax2.php?id2=" + id2);
}

How to create a xmlhttp request?

var url="display.php?vote="+grade;
xmlHttp.onreadystatechange=stateChanged
xmlHttp.open("GET",url,true)
xmlHttp.send(null)
}
}
function stateChanged()
{
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
{
document.getElementById("txtHint").innerHTML=xmlHttp.responseText
}
}
This piece of code fails to send out the request. How to create a xmlHttp correctly?

<script type="text/javascript">
function ajaxFunction()
{
var xmlhttp;
if (window.XMLHttpRequest)
{
// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else if (window.ActiveXObject)
{
// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
else
{
alert("Your browser does not support XMLHTTP!");
}
}
</script>
this piece of code is available in link text you can learn basics here like i did. hope this helps.

Here is a "80%" solution.
function GetXHR()
{
try
{
if (window.XmlHTTPRequest)
xmlHttp = new XmlHTTPRequest()
else
xmlHttp = new ActiveXObject("MSXML2.XMLHTTP.3.0")
}
catch(e) { }
}
var xmlHttp = GetXHR()
if (xmlHttp)
{
// Proceed with xmlHttp usage.
}
Edit
Note I tend to avoid the old ProgID "Microsoft.XMLHTTP" in favour of the one I have used because this later ProgID has a more predictable behaviour and is ever so slightly more secure. However if you want wider compatiblity with really old Windows machines (I'm talking out-of-support stuff) then you could use the older one in your specific case.

var xmlHttp=new(window.ActiveXObject?ActiveXObject:XMLHttpRequest)('Microsoft.XMLHTTP');