Develop Reference

'Cross Origin' error message resulting from local XmlHttpRequest

I am using AJAX to display upcoming events on a website. To that end, I call a JavaScript function via onload="showEvents(3);", see the function below:
function showEvents (amount) {
// are there Events?
if (document.getElementById("eventsDiv")) {
document.getElementsByClassName("info")[0].innerHTML = 'Loading events...';
// initialize XML Http Request
var xmlhttp;
if (window.XMLHttpRequest) {
xmlhttp = new XMLHttpRequest();
} else {
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange = function () {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
document.getElementById("eventsDiv").innerHTML = xmlhttp.responseText;
}
}
// send request
xmlhttp.open("GET", "./events.php?number=" + encodeURIComponent(amount), true);
xmlhttp.setRequestHeader("Content-Type", "text/plain;charset=UTF-8");
xmlhttp.send();
}
}
The file events.php is a PHP file in the same directory, and it connects to the database to fetch the upcoming events. The HTML header of the main website includes
<base href="http://www.my-domain.com/">
The problem: I get a "Cross Orign" error message (in Firefox), preventing my parent index.html file accessing the events.php. As I understand, this error message should not appear since I am using a resource from the same directory.

Ok that's ok, you also can do like this...
if($_SERVER['HTTP_ORIGIN'] == "http://your-domain.com") {
header('Access-Control-Allow-Origin: http://your-domain.com');

same domain xmlhttprequest access denied ie8

I'm fairly new to the world of web development and am trying to read a txt file in internet explorer 8 and compare it to source code of a website to see if they are equal. This is so I can work out if the web page is functioning correctly.
I managed to get the source code with an xmlhttprequest and have tried the same to get the text file (which is in the same domain as my web page) and I am getting an access denied error.
After some research I can see that cross-domain xmlhttprequests won't work but that's not what I'm trying to do so I'm not sure how to proceed.
Having run the same code in Firefox(current version). It will read the file but not the web page!
I don't mind which of the two browsers I end up using but at the moment each does half of what I want it to.
my code is:
function source1(){
xmlhttp=new XMLHttpRequest();
xmlhttp.open("GET", "http://website",true);
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState==4) {
document.getElementById('textzone').value = xmlhttp.responseText
var inputString = xmlhttp.responseText;
alert(inputString);
comparison(inputString)
}
}
xmlhttp.send(null)
}
function comparison(inputString){
xmlhttp1=new XMLHttpRequest();
xmlhttp1.open("GET", "comparisondoc.txt", false);
xmlhttp1.onreadystatechange=function() {
if (xmlhttp1.readyState==4) {
var compareString = xmlhttp1.responseText;
alert(compareString)
if(inputString==compareString){
alert("Strings are equal");
}
}
}
xmlhttp.send(null)
}
All I need to know is why either the file won't open in ie8, or why the website source code shows up blank (in the alert) in firefox. Any help would be appreciated.

It could be a browser support issue.
Try the following code to initialize your XMLHttpRequest :
function createRequest() {
try {
request = new XMLHttpRequest();
} catch (trymicrosoft) {
try {
request = new ActiveXObject("Msxml2.XMLHTTP");
} catch (othermicrosoft) {
try {
request = new ActiveXObject("Microsoft.XMLHTTP");
} catch (failed) {
request = false;
}
}
}
if (!request)
alert("Error initializing XMLHttpRequest!");
}

Check your comparison function. You should you xmlhttp1 instead of xmlhttp at 2 places
function comparison(inputString){
xmlhttp1=new XMLHttpRequest();
xmlhttp1.open("GET", "comparisondoc.txt", false);
xmlhttp1.onreadystatechange=function() {
if (xmlhttp1.readyState==4) {
<!--alert(xmlhttp1.responseText)-->
var compareString = xmlhttp1.responseText;
alert(compareString)
if(inputString==compareString){
alert("Strings are equal");
}
}
}
xmlhttp1.send(null)
}

Try to add the if(xmlhttp.status == 200) { } stuff. Remember both of these are looping through status' "AND" readystates.
Technically you could be erroring somewhere (I'd rather not speculate on) halting progress to next request or whatever without the status check.
Also you "should" try other request techniques. ie.. xmlhttp.onreadystatechange = function(){itsReady(inputString)}; // we keep this line short and simple calling to another func that contains your status and readystate checks, response stuff, and more func.
On a pretty normal run the Loop looks like:
hi rdySte:1///status 0////////
hi rdySte:2///status 200////////
hi rdySte:3///status 200////////
hi rdySte:4///status 200////////
I ran into a lot of weird issues trying the long onreadystatechange = function (){ ... All stuff..} I successfully run a crazy set of request functionalities using the short onreadystatechange technique.
I noticed at the last minute->
is there a reason why the async flags are different between your funcs? I'd set them all to true unless you have a great reason.
This will work: (to test: 2 pages t1.php contains a num or whatever and t2.txt that has a num in sam dir as the funcs are called in)
function source1(){
var avar = 1;
xmlhttp=new XMLHttpRequest();
xmlhttp.open("GET", "t1.php",true); // shortened f-names for ease of test
xmlhttp.onreadystatechange = function(){jsg_snd(avar)};
xmlhttp.send(null)
}
function jsg_snd(avar){
if (xmlhttp.readyState==4) {
if (xmlhttp.status == 200) {
var inputString = xmlhttp.responseText;
document.getElementById('text_zone').innerHTML = inputString;
document.getElementById('text_zone1').value = inputString;
// alert(inputString);//
comparison(inputString)
}
}
}
function comparison(inputString){
xmlhttp1=new XMLHttpRequest();
xmlhttp1.open("GET", "t2.txt", true);
xmlhttp1.onreadystatechange= function(){jsg_snd1(inputString);};
xmlhttp1.send(null)
}
function jsg_snd1(inputString){
if (xmlhttp1.readyState==4) {
if (xmlhttp1.status == 200) {
var compareString = xmlhttp1.responseText;
//alert(compareString)
if(inputString==compareString){
//alert("Strings are equal");
document.getElementById('text_zone').innerHTML += "; Ok "+inputString+"=="+compareString+"";
}
}
}
}
Now the html in your body should look like:
<tt id = 'text_go' onMouseUp="source1();" >Go!</tt>
<tt id = 'text_zone' onMouseUp="text_zone.innerHTML = '';" >Click to clear!</tt>
<input type ='text' id = 'text_zone1' onMouseUp="text_zone1.value = '';" value = 'Click to clear!' >
The extra stuf is for ___s & giggles.

Ajax Pull Content From another webpage

So I got this code for pulling rss feeds from another website (i asked them, and they gave me permission) I Don't know what should i Write in TAG1 and TAG2. Basically that is just my problem:
Here is the html (its an ajaxed page)
<!doctype html>
<html lang="hu">
<head>
<title>Videók</title>
<meta charset="utf-8"/>
<script type="text/javascript" src="../js/videok.js"></script>
</head>
<body>
<h2>Van egy jó videód? Töltsd fel és kikerülhet az oldalra!</h2>
<div id="videok"></div>
</body>
</html>
And here is the Javascript for pulling
window.onload = initAll;
var xhr = false;
var dataArray = new Array();
var url = "choose url";
function initAll() {
if (window.XMLHttpRequest) {
xhr = new XMLHttpRequest();
}
else {
if (window.ActiveXObject) {
try {
xhr = new ActiveXObject("Microsoft.XMLHTTP");
}
catch (e) { }
}
}
if (xhr) {
xhr.onreadystatechange = setDataArray;
xhr.open("GET", url, true);
xhr.send(null);
}
else {
alert("couldn't create XMLHttpRequest");
}
}
function setDataArray() {
var tag1 = "subject1";
var tag2 = "subject2";
if (xhr.readyState == 4) {
if (xhr.status == 200) {
if (xhr.responseXML) {
var allData = xhr.responseXML.getElementsByTagName(tag1);
for (var i=0; i<allData.length; i++) {
dataArray[i] = allData[i].getElementsByTagName(tag2)[0].firstChild.nodeValue;
}
}
}
else {
alert("the request failed" + xhr.status);
}
}
}

You won't be able to use javascript to pull from another web page because javascript is sandboxed when in browsers. Sandboxing means that you will only be able to send requests to the same domain that the javascript originally came from (also known as the 'same orgin policy').
You can use a serverside language like php to do the pulling and then hand it down to the javascript through ajax.
The code that you posted looks like it just makes a simple ajax call but it shouldn't work when trying to request an RSS from anything other than your own site.

It's better that you have the server side of your application fetch data for the xml and format the data how you want it.
You would have the Ajax request hit your server's end point, then your server will fetch the xml data, format it properly and respond to the request with the correct formatted data.

How to refresh a part of a web page using Javascript or using jQuery?

How can I refresh a particular part of a web page with a time interval (not entire page)?

You can use Ajax for your purpose.
suppose you want to check username availability before registering a user to your site.
create a request object asynchronously
function createRequest()
{
try{
request=new XMLHttpRequest();
} catch(tryMS){
try{
request=new ActiveXObject("Msxml2.XMLHTTP");
} catch(otherMS){
try{
request=new ActiveXObject("Microsoft.XMLHTTP");
} catch(failed) {
request=null;
}
}
}
return request;
}
Next is the code to send a asynchronous request
function checkAvailability (username) {
request=createRequest();
if(request==null){
alert("Ajax request not possible on your browser");
return;
}
var url="checkAvailability?username="+username;
request.open("GET", url, true);
request.onreadystatechange = showStatus;
request.send(null);
}
Track the response
function showStatus () {
if(request.readyState == 4) {
if(request.status == 200) {
var response = request.responseText;
if(response == 1){
//username available
} else{
//username not available
}
}
}
}

Suppose you have a DIV in your your Web Page that you want to refresh :
<div id="myDiv"> </div>
To refresh it using javascript you just have to select it and change the html code :
document.getElementById("myDiv").innerHtml = "Your new html code to display"
If you want to deal with forms, database queries ...
You have to use AJAX to call some php scripts for example without reloading the current page ...

You are talking about AJAX
Look at http://api.jquery.com/jQuery.ajax/ for jQuery
But please consider learning the underlying javascript language - you will be better for it in the long run
here is a simple example
http://www.degraeve.com/reference/simple-ajax-example.php
The history behind ajax can be found here http://www.adaptivepath.com/ideas/ajax-new-approach-web-applications

send an http request without XHR in an event handler

How to send an http request with either post/get method using javascript as an eventhandler? Thanks! Paul

Okay, you don't want to use Ajax.
You can use an event handler to submit a form!
<a href='#' onclick='cow_submit("zoodle")'>send</a>
<form method='post' id='formie' action='find_some_action.php'>
<input type='hidden' id='snoutvar' name='snoutvar' value='snout'>
</form>
<script>
function cow_submit(a_var_to_set){
var plip=document.getElementById('formie');
var snout=document.getElementById('snoutvar');
snout.value=a_var_to_set;
plip.submit();
}
See https://developer.mozilla.org/en/DOM/form

use XmlHttpRequest
sample code:
var client = new XMLHttpRequest();
client.onreadystatechange = handler;
client.open("GET", "test.xml");
client.send();
function handler()
{
// your handler
}

You can use XMLHttpRequest for sending request from javascript
Sending GET request
var url = "get_data.php";
var params = "lorem=ipsum&name=binny";
http.open("GET", url+"?"+params, true);
http.onreadystatechange = function() {//Call a function when the state changes.
if(http.readyState == 4 && http.status == 200) {
alert(http.responseText);
}
}
http.send(null);
Sending POST request
var url = "get_data.php";
var params = "lorem=ipsum&name=binny";
http.open("POST", url, true);
//Send the proper header information along with the request
http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
http.setRequestHeader("Content-length", params.length);
http.setRequestHeader("Connection", "close");
http.onreadystatechange = function() {//Call a function when the state changes.
if(http.readyState == 4 && http.status == 200) {
alert(http.responseText);
}
}
http.send(params);
And don't forget to encode parameters using encodeURIComponent for param value encoding in case of user input
e.g.
params="paramName="+encodeURIComponent(paramValue);

The standard class for doing this is XmlHttpRequest, but it's not universally supported. On some browsers you have to use ActiveXObject("Microsoft.XMLHTTP") instead.
Look into the jQuery system which provides HTTP download (AJAX style) methods regardless of the underlying browser APIs (hence avoiding a lot of the code shown in Tzury's answer).
The jQuery AJAX documentation is at http://docs.jquery.com/Ajax

You should try to add atring in a hidden field and then call the form.submit() to submit your form into the page define in action.
<script type="text/javascript">
function doTestFormSubmit(yourString) {
document.getElementById("myString").value=myString;
document.getElementById("testForm").submit();
}
</script>
<form name="testForm" id="testForm" action="yourDesiredPage.php" method="post">
<input type="hidden" name="myString" id="myString" value=""/>
</form>

Ajax Tutorial (http://code.google.com/edu/ajax/tutorials/ajax-tutorial.html)
var obj;
function ProcessXML(url) {
// native object
if (window.XMLHttpRequest) {
// obtain new object
obj = new XMLHttpRequest();
// set the callback function
obj.onreadystatechange = processChange;
// we will do a GET with the url; "true" for asynch
obj.open("GET", url, true);
// null for GET with native object
obj.send(null);
// IE/Windows ActiveX object
} else if (window.ActiveXObject) {
obj = new ActiveXObject("Microsoft.XMLHTTP");
if (obj) {
obj.onreadystatechange = processChange;
obj.open("GET", url, true);
// don't send null for ActiveX
obj.send();
}
} else {
alert("Your browser does not support AJAX");
}
}
function processChange() {
// 4 means the response has been returned and ready to be processed
if (obj.readyState == 4) {
// 200 means "OK"
if (obj.status == 200) {
// process whatever has been sent back here:
// anything else means a problem
} else {
alert("There was a problem in the returned data:\n");
}
}
}