XMLHttpRequest.readyState - javascript

home.html
front page test
test.php
<SCRIPT language="JavaScript" SRC="ajax.js"></SCRIPT>
<button type="button" onclick="callAJAX('home.html','displaydiv')">Click Me!</button>
<div id="displaydiv"></div>
ajax.js
function callAJAX(url, pageElement, callMessage) {
document.getElementById(pageElement).innerHTML = callMessage;
try {
req = new XMLHttpRequest(); /* e.g. Firefox */
} catch(e) {
try {
req = new ActiveXObject("Msxml2.XMLHTTP");
/* some versions IE */
} catch (e) {
try {
req = new ActiveXObject("Microsoft.XMLHTTP");
/* some versions IE */
} catch (E) {
req = false;
}
}
}
req.onreadystatechange = function() {responseAJAX(pageElement);};
req.open("GET",url,true);
req.send(null);
}
function responseAJAX(pageElement) {
console.log(req.readyState);
var output = '';
if (req.readyState == 4) {
if (req.status == 200) {
output = req.responseText;
document.getElementById(pageElement).innerHTML = output;
}
}
}
Above code is mainly from here:
Questions:
according to this site, onreadystatechange stores a function (or the name of a function) to be called automatically each time the readyState property changes so when will readyState property change? after req.send(null);?
for this line: console.log(req.readyState); in chrome console, it shows: 1 2 3 4, it does not output 0, is that because 0: request not initialized?

readyState changes in a few places, check out Mozilla's documentation for more information. req.readyState = 0 means that req.open() has not been called yet.
Also, depending on what browsers you are trying to support with this code, you can look into using some of the features from XHR2, including a req.onload() function that would change your code to:
function callAJAX(url, pageElement, callMessage) {
var elem = document.getElementById(pageElement);
elem.innerHTML = callMessage;
var req = new XMLHttpRequest();
req.onload = function() {
elem.innerHTML = req.responseText;
};
req.open("GET",url,true);
req.send(null);
}

Related

Web Workers and JSON

I am sure there is something that I am missing from this code, I just can not figure out what it is.
Here is the main page:
<script>
function wwCallback(e) {
document.write(e.data);
}
function wwError(e) {
alert(e.data)
}
$(document).ready(function () {
var worker = new Worker("sync.js");
worker.onmessage = wwCallback;
worker.onerror = wwError;
worker.postMessage({
'cmd': 'downloadUser',
'url': 'server.php'
});
console.log("WW Started");
});
</script>
Server.php simply echoes a JSON string and I have verified that it is both valid and working using normal ajax requests.
Here is my web workers code:
function getData(url) {
var req = new XMLHttpRequest();
//expect json
req.open('GET', url);
req.send(null);
req.onreadystatechange = function () {
if (req.readyState == 4) {
if (req.status == 200) {
self.postMessage(req.responseText);
}
}
}
}
self.addEventListener('message', function (e) {
var data = e.data;
switch (data.cmd) {
case 'downloadUser':
getData(data.url);
}
self.close();
}, false);
Could anyone point me in the right direction?
Your problem is in your WebWorker XHR call. You've opened the request, then immediately sent it before you've set up the event handler to handle the response. You just need to move the req.send(null); call below the code that sets up the event handler.
Try this:
function getData(url) {
var req = new XMLHttpRequest();
//expect json
req.open('GET', url);
// req.send(null); // remove this line from here.
req.onreadystatechange = function () {
if (req.readyState == 4) {
if (req.status == 200) {
self.postMessage(req.responseText);
}
}
}
req.send(null); // make the request after your readystatechange
// handler is set up.
}
self.addEventListener('message', function (e) {
var data = e.data;
switch (data.cmd) {
case 'downloadUser':
getData(data.url);
}
self.close();
}, false);

javascript insertBefore method results to "NotFoundError: An attempt was made to reference a Node in a context where it does not exist."

here is my html:
<html><body>
page starts here
this is a test page
top:
<script id="invoc_code" type="text/javascript">
window.onload = function() {
var xhr;
if (window.XMLHttpRequest) {
xhr = new XMLHttpRequest();
} else {
xhr = new ActiveXObject("Microsoft.XMLHTTP");
}
xhr.onreadystatechange = function() {
var body = document.body;
if (xhr.readyState == 4 && xhr.status == 200) {
if(body.firstChild){
body.insertBefore(xhr.response, body.firstChild);
} else {
body.appendChild(xhr.response);
}
}
};
xhr.open("GET", "http://google.com", true);
xhr.send();
};
</script>;
page ends here
</body></html>
line body.insertBefore(xhr.response, body.firstChild); results to "NotFoundError: An attempt was made to reference a Node in a context where it does not exist". Can you please tell me what is the reason?
Thanks in advance
The insertBefore method expects a DOM element as its first parameter. If the XHR response is a HTML string, then you need to create one using this. Depending on your required DOM output you could do something like this:
var newElem = document.createElement("div");
newElem.innerHTML = xhr.response;
body.insertBefore(newElem, body.firstChild);

PUT/DELETE XMLHttpRequest Not Working in Firefox

I am working with javascript cross domain ajax request. my code is working fine on chrome and other devices like android browser and android native app using phonegap.
But i was facing issue with Firefox..
Firefox does not support my PUT and DELETE requests.
Is there any solution for firefox to make put and delete request to my server.
firefox does support my post and get request. both request working fine.
here is my working code.
var XMLHttpFactories = [
function () {
return new XMLHttpRequest()
},
function () {
return new ActiveXObject("Msxml2.XMLHTTP")
},
function () {
return new ActiveXObject("Msxml3.XMLHTTP")
},
function () {
return new ActiveXObject("Microsoft.XMLHTTP")
}
];
function createXMLHTTPObject() {
var xmlhttp = false;
for (var i=0;i<XMLHttpFactories.length;i++) {
try {
xmlhttp = XMLHttpFactories[i]();
}
catch (e) {
continue;
}
break;
}
return xmlhttp;
}
For send Put request..
var xhr = createXMLHTTPObject();
xhr.open("PUT", url,true);
xhr.onreadystatechange=function()
{
if (xhr.readyState==4)
{
if(xhr.status==200){
request.success(xhr.responseText);
}else if(xhr.status!=200){
request.error(xhr.responseText)
}
}
}
xhr.send(body);
The following is working just fine on Firefox 22.0 (& 23.0 too):
var XMLHttpFactories = [
function () {
return new XMLHttpRequest()
},
function () {
return new ActiveXObject("Msxml2.XMLHTTP")
},
function () {
return new ActiveXObject("Msxml3.XMLHTTP")
},
function () {
return new ActiveXObject("Microsoft.XMLHTTP")
}
];
function createXMLHTTPObject() {
var xmlhttp = false;
for (var i=0;i<XMLHttpFactories.length;i++) {
try {
xmlhttp = XMLHttpFactories[i]();
}
catch (e) {
continue;
}
break;
}
return xmlhttp;
}
var xhr = createXMLHTTPObject();
xhr.open("PUT", "/echo/html/", true);
xhr.onreadystatechange = function()
{
if (xhr.readyState == 4)
alert("Request completed, with the following status code: " + xhr.status);
}
xhr.send("");
Here is a jsFiddle: http://jsfiddle.net/qXQtD/
To better understand your situation, please answer the following:
What is the data you are trying to send?
What are your complete response headers (especially the "Access-Control-Allow-Origin" header)?

Ajax not working in firefox without alert

function processAjaxStateChangeForRowAdd() {
alert(0);
if (req.readyState == 4) { // Complete
if (req.status == 200) { // OK response
processForRowAdd(req.responseText);
} else {
alert("Problem: " + req.statusText);
}
}
}
This code is working fine for IE, Safari and Firefox, but if I remove the alert, then the code will not work in Firefox, though it still works in IE and Safari.
Can anybody give me suggestion why it not working in Firefox without alert?
EDIT: Code that adds a row:
if (window.XMLHttpRequest && browserVersion.indexOf("Microsoft") == -1 ) {
// code for Firefox, Chrome, Opera, Safari
req = new XMLHttpRequest("");
if (req) {
ajaxProcessed = false;
req.onreadystatechange = processAjaxStateChangeForRowAdd;
req.open("POST", url, true);
req.send();
// alert("1");
}
}
The alert is blocking. What this means is that your script is temporarily suspended (even if it's for a few milliseconds). During this time, your AJAX request completes and your req object is being set. You can add a delay (using setTimeout) to your callback to verify this.
I would suggest you post more of your script so that we can help you set up your callback properly. Alternatively, use a library such as jQuery to set up AJAX calls in a cross-browser manner easily.
EDIT: You need to either declare req as a global variable, or use an anonymous function. The following code demonstrates the first method (using a global variable):
var req;
if (window.XMLHttpRequest) {
req = new XMLHttpRequest();
if (req) {
req.onreadystatechange = processAjaxStateChangeForRowAdd;
req.open("POST", url, true);
req.send();
}
}
function processAjaxStateChangeForRowAdd() {
if (req.readyState == 4) { // Complete
if (req.status == 200) { // OK response
processForRowAdd(req.responseText);
} else {
alert("Problem: " + req.statusText);
}
}
}
function getHttp()
{
var xmlhttp;
try
{
xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
}
catch(e)
{
try
{
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
catch(e)
{
if(typeof XMLHttpRequest != 'undefiend')
{
xmlhttp = new XMLHttpRequest();
}
}
}
return xmlhttp;
}
can you try this:
if (request.readyState == 4) {
if (request.status == 200) {
var response = request.responseText;
} else
alert("status: " + request.status);
}
You should also check for the readyState , the following code might help
req.onreadystatechange=function()
{
if (req.readyState==4 && req.status==200)
{
processForRowAdd(req.responseText)
}
}
Read this for the different values of readyState

Dynamically change a div's ID?

I have a bunch of divs with weird id and each of them contains a video. They're actually video embed codes but they're not usual to me. Here's one example:
<div id="evp-1fae4e37639894816f03591bc7009c68-wrap" class="evp-video-wrap"></div><script type="text/javascript" src="http://domain.com/evp/framework.php?div_id=evp-1fae4e37639894816f03591bc7009c68&id=cmVsYXRpb25zaGlwLW1hcmtldGluZy0xLmZsdg%3D%3D&v=1278525356"></script><script type="text/javascript">_evpInit('cmVsYXRpb25zaGlwLW1hcmtldGluZy0xLmZsdg==');</script>
What I want to do is create a video playlist. As a part of that, I created list using divs also which use the onclick attribute to trigger my JS function to switch between videos. Here's how it looks:
<div class="vid-list" onclick="switchvideo('http://domain.com/html-vids/headline-vids/second-vid.html', 2)"><p>This a video tutorial for blah blah blah.</p></div>
The problem is, each time I switch to another video the div id of the embed code changes also because otherwise it won't work. So I need to change that before loading the video script inside the div. I tried to achieve that using the following JS function:
function switchvideo(url, vidnumber)
{
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
xmlhttp.open("GET",url,false);
xmlhttp.send(null);
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
xmlhttp.open("GET",url,false);
xmlhttp.send();
}
var div_node = document.getElementByClass('evp-video-wrap');
if ( vidnumber == 2 ) {
div_node.id = 'evp-78c0b7c4f6d3377954825f145734fd5c-wrap';
}
document.getElementById(div_node.id).innerHTML=xmlhttp.responseText;
}
Apparently it's not working. I suspect the problem are the lines in bold above. I tried to get the element by 'class' and its id by using 'div_node.id'. I am assuming that by doing 'document.getElementByClass', I am getting the reference to that element so I could use it to manipulate its other attributes. But I am not sure... Could anyone pls enlighten me??
There is no getElementByClass() method. There is a getElementByClassName() but it's not available in every browser.
Here is one you can use:
// http://www.dustindiaz.com/getelementsbyclass/
function getElementsByClass(searchClass, node, tag) {
var classElements = new Array();
if (node == null) node = document;
if (tag == null) tag = '*';
var els = node.getElementsByTagName(tag);
var elsLen = els.length;
var pattern = new RegExp("(^|\\s)" + searchClass + "(\\s|$)");
for (i = 0, j = 0; i < elsLen; i++) {
if (pattern.test(els[i].className)) {
classElements[j] = els[i];
j++;
}
}
return classElements;
}
Then you can call it as
getElementByClass('evp-video-wrap');
Your ajax is a bit tricky, but here is a more general one:
function getXmlHttpObject() {
var xmlHttp;
try {
// Firefox, Opera 8.0+, Safari
xmlHttp = new XMLHttpRequest();
} catch (e) {
// Internet Explorer
try {
xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
}
if (!xmlHttp) {
alert("Your browser does not support AJAX!");
}
return xmlHttp;
}
function ajax(url, onSuccess, onError) {
var xmlHttp = getXmlHttpObject();
xmlHttp.onreadystatechange = function() {
if (this.readyState === 4) {
// onSuccess
if (this.status === 200 && typeof onSuccess == 'function') {
onSuccess(this.responseText);
}
// onError
else if(typeof onError == 'function') {
onError();
}
}
};
xmlHttp.open("GET", url, true);
xmlHttp.send(null);
return xmlHttp;
}
Finally your code becomes:
function switchvideo(url, vidnumber) {
var div_node = getElementByClass('evp-video-wrap')[0];
// make a call to the url, and execute the
// callback when the response is available
ajax(url, function( responseText ){
if (vidnumber == 2) {
div_node.id = 'evp-78c0b7c4f6d3377954825f145734fd5c-wrap';
}
document.getElementById(div_node.id).innerHTML = responseText;
});
}​
You can see the whole code [here]
getElementByClass isn't a standard method. Is it possible for you to use a framework for this? jQuery has a nice mechanism to search for an element by class, as do the other frameworks. It also makes it much easier to do the AJAX bits in a cross-browser supported way.
function switchvideo(url, vidnumber)
{
$.get(url, function(data) {
var div_node = $('.evp-video-wrap');
if (vidnumber == 2) {
div_node.attr('id', 'evp-78c0b7c4f6d3377954825f145734fd5c-wrap');
}
div_node.html( data );
});
}
An alternative would be to write your own getElementByClass or specific code to search for a DIV by class. Note: I assume you're only interested in the first match.
function getDivByClass( klass )
{
var regex = new RegExp( '(^|\\s+)' + klass + '(\\s+|$)' );
for (div in document.getElementsByTagName('div')) {
if (regex.text( div.className)) {
return div;
}
}
return null;
}

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