I'm trying to make an AJAX GET request, but I simply cannot get it to work. I want to retrieve the HTML source of example.com. I've previously used JQuery to send AJAX requests, but I use JQuery only for its AJAX capabilities so it's a waste to include the 30KB file for one task. What is it that I'm doing wrong?
<script type="text/javascript">
var XMLHttpArray = [
function() {return new XMLHttpRequest()},
function() {return new ActiveXObject("Msxml2.XMLHTTP")},
function() {return new ActiveXObject("Msxml2.XMLHTTP")},
function() {return new ActiveXObject("Microsoft.XMLHTTP")}
];
function createXMLHTTPObject(){
var xmlhttp = false;
for(var i=0; i<XMLHttpArray.length; i++){
try{
xmlhttp = XMLHttpArray[i]();
}catch(e){
continue;
}
break;
}
return xmlhttp;
}
function AjaxRequest(url,method){
var req = createXMLHTTPObject();
req.onreadystatechange= function(){
if(req.readyState != 4) return;
if(req.status != 200) return;
return req.responseText;
}
req.open(method,url,true);
req.send(null);
}
function MakeRequst(){
var result=AjaxRequest("http://example.com","get");
alert(result);
}
</script>
Returning a value from your state change handler won't do you any good - that code is waiting for something to happen, and it's invoked from the browser innards as the HTTP request is processed. It's asynchronous.
Instead of expecting a result like that, your state change handler must itself handle the response, as appropriate to your application.
function AjaxRequest(url,method){
var req = createXMLHTTPObject();
req.onreadystatechange= function(){
if(req.readyState != 4) return;
if(req.status != 200) return;
alert(req.responseText);
}
req.open(method,url,true);
req.send(null);
}
Related
I have created some little jt code, but it gives me error
function Mind(){
var request = "request";
var reply = "reply";
var words = '';
this.Reply = function(){
if(request == words.nouns[0].noun){
reply = words.nouns[0].noun;
}
else
reply = this.words.nouns[0].noun;
}
this.SetRequest = function(req){
request = req;
}
this.GetReply = function(){
return reply;
}
this.Parse = function(u){
var xmlhttp = new XMLHttpRequest();
var url = u;
var result;
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
words = JSON.parse(xmlhttp.responseText);
}
}
xmlhttp.open("GET", url, true);
xmlhttp.send();
return result;
}
this.Construct = function(){
words = this.Parse('mind/words.json');
}}
var mind = new Mind();
mind.Parse('mind/words.json');
and here is my json file
{
"nouns": [
{"noun": "child"},
{"noun": "father"}
]
}
In command live all goes well, but when I run this code, appears error
Uncaught TypeError: Cannot read property 'nouns' of undefined
Mutliple errors. The most fundamental one is that your code ignores that XMLHttpRequest is async, and wont return a value in the same way as "regular" functions. Read about it here: How to make a function wait until a callback has been called using node.js. The TL;DR is that you have to pass in a "callback-function" to your parse-method and "return" your value using that function, instead of using a return-statement. Google for "javascript callbacks" and read a few tutorials if this concept is new to you!
You also have some minor errors, like returning result from Parse, but never actually setting result to anything. Also words is being assigned in multiple places in a way that doesn't really make sense. But both of these things will go away when you solve the sync/async issues.
EDIT:
Essentially the fix looks like this:
this.Parse = function(u, callback){ // this "callback" is new
var xmlhttp = new XMLHttpRequest();
var url = u;
var result;
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
words = JSON.parse(xmlhttp.responseText);
callback(null, words); // we're "returning" the words here
}
}
xmlhttp.open("GET", url, true);
xmlhttp.send();
// no return statement here!
}
this.Construct = function(){
this.Parse('mind/words.json', function(error, words) {
// here you can use your words!
});
}}
At the moment I am calling a function on a setInterval basis.
This function makes a XMLHttpRequest to my server to get update info. If there is an update available I update an image (using canvas element).
Is this the optimum way to do this sort of thing?
My code:
Calling code:
function StartFeedUp() {
if (tmrStartFeedUp) window.clearInterval(tmrStartFeedUp);
tmrStartFeedUp = setInterval(GetNextImage, 330);
}
My called function:
var isProcess = false;
function GetNextImage() {
try {
if (!isProcess) {
isProcess = true;
var urlTS = '/Cloud/isNewFrames.ashx?alias=' + alias + '&version=' + version + '&guidlogon=' + guidlogon;
var xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET", urlTS, true);
xmlhttp.timeout = 200;
xmlhttp.send();
var nextts = xmlhttp.responseText;
}
isProcess = false;
}
catch (err) {
isProcess = false;
document.getElementById("divMode2").innerHTML = err;
}
}
Other than repeating the XHR call, you can use HTML5 Web Sockets which allows you to maintain a connection to the server, whereby the server would push data as and when needed. Web Sockets are relatively new and so aren't supported by old browsers.
Your XHR is asyncronous so you should be listening on the onreadystatechange event instead of always expecting the response to be available directly after the send() call:
xmlhttp.open("GET", urlTS, true);
xmlhttp.timeout = 200;
xmlhttp.onreadystatechange = function(){
if(xmlhttp.readyState == 4 && xmlhttp.status == 200){
console.log("received " + xmlhttp.responseText);
}
}
xmlhttp.send();
I'm trying to wait for the AJAX request to complete. It would be easy if the method xmlhttp.open would support async = false but Ant Galio does not support this option and only asynchronous requests are permitted. The question is how can I wait for the callback to be called.
var ajaxFinished = false;
var xmlhttp = new XMLHttpRequest();
this.debug("-- onreadystatechange is being defined");
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4) {
ajaxFinished = true;
var data = xmlhttp.responseText;
if (xmlhttp.status == 200) {
that.debug('downloadSettings: SUCCESS');
[...]
} else {
that.debug('downloadSettings:');
that.debug('-- Error: ');
that.debug('-- ResponseText: "'+data+'"')
}
}
}
while (ajaxFinished == false) {
}
this.debug("-- open connection");
xmlhttp.open("GET", requestUrl, true); /* Ant Galio does not support synchronous */
this.debug("-- send");
xmlhttp.send();
I'm looking for some kind of active waiting. I know about another solution but I'm interested in a solution that would not require changing more of the code than is my example above.
Thanks!
yes, you can
function getFile(url) {
if (window.XMLHttpRequest) {
AJAX=new XMLHttpRequest();
} else {
AJAX=new ActiveXObject("Microsoft.XMLHTTP");
}
if (AJAX) {
AJAX.open("GET", url, false);
AJAX.send(null);
return AJAX.responseText;
} else {
return false;
}
}
var fileFromServer = getFile('http://somedomain.com/somefile.txt');
w3c definition http://www.w3.org/TR/XMLHttpRequest/#the-open()-method
client . open(method, url [, async = true [, user = null [, password = null]]])
You can't. There is no "active waiting" in JavaScript, there can be only one active execution a time ("single-threaded").
There is a workaround.
Instead of using the the blocking while loop for poll use the nonblocking setInterval()..
so your code might look something like this.
var ajaxFinished = false;
var xmlhttp = new XMLHttpRequest();
this.debug("-- onreadystatechange is being defined");
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4) {
ajaxFinished = true;
var data = xmlhttp.responseText;
if (xmlhttp.status == 200) {
that.debug('downloadSettings: SUCCESS');
[...]
} else {
that.debug('downloadSettings:');
that.debug('-- Error: ");
that.debug('-- ResponseText: "'+data+'"')
}
}
}
//Polling function
function checkEvent(){
if(ajaxFinished == true){
//your code i.e xmlhttp.open("GET", requestUrl, true);
}
clearInterval(chkeventid);//Clear Interval via ID for single time execution
}
var chkeventid=self.setInterval("checkEvent()",100);//The poll call
The setInterval method is treated a bit differently in JS as you know so you may use it as against the while loop.
hello i have problem to parse xml..
i have xml like this :
<tejemahan>
<kategori> komputer </kategori>
<hasil> aplikasi komputer </hasil>
</terjemahan>
Edited:
xml above I get in that way :
var url="http://localhost:8080/inlinetrans/api/translate/"+userSelection+"/"+hasilStemSel+"/"+hasilStem;
var client = new XMLHttpRequest();
client.open("GET", url, false);
client.setRequestHeader("Content-Type", "text/plain");
client.send(null);
if(client.status == 200)
alert("the request success"+client.responseText);
else
alert("the request isn't success"+client.status+""+client.statusText)
}
and this is my code to parse an xml file above :
this.loadXML = function (){
var url = http://localhost:8080/coba/api/artikan/"+sel+"/"+hasilStemSel+"/"+hasilStem
xmlDoc=document.implementation.createDocument("","",null);
xmlDoc.load("url");
xmlDoc.onload= this.readXML;
}
this.readXML = function() {
alert(xmlDoc.documentElement.tagName);
alert(xmlDoc.documentElement.childNodes[0].tagName);
alert(xmlDoc.documentElement.childNodes[1].tagName);
alert(xmlDoc.documentElement.childNodes[0].textContent);
alert(xmlDoc.documentElement.childNodes[1].textContent);
}
i can execute this code
xmlDoc=document.implementation.createDocument("","",null);
xmlDoc.load("url");
but why i can't execute this code
xmlDoc.load = this.readXML ???
Try putting the onload handler assignment before the load() call. If you call load() first, the onload event will happen before you have assigned a handler to handle it. Like this:
xmlDoc=document.implementation.createDocument("","",null);
xmlDoc.onload= this.readXML;
xmlDoc.load("url");
Firstly, I second David Dorward's suggestion: use XMLHttpRequest instead, which will work in all major browsers. Code is below.
Secondly, your readXML function is flawed, since most browsers will include whitespace text nodes within the childNodes collection, so xmlDoc.documentElement.childNodes[0] will actually be a text node and have no tagName property. I would suggest using getElementsByTagName() or checking the nodeType property of each node as you iterate over childNodes.
Thirdly, your XML is not valid: the <tejemahan> and </terjemahan> do not match, although this may be a typo in your question.
var url = "http://localhost:8080/coba/api/artikan/"+sel+"/"+hasilStemSel+"/"+hasilStem;
var readXML = function(xmlDoc) {
alert(xmlDoc.documentElement.tagName);
var kategori = xmlDoc.getElementsByTagName("kategori")[0];
alert(kategori.tagName);
};
var createXmlHttpRequest = (function() {
var factories = [
function() { return new XMLHttpRequest(); },
function() { return new ActiveXObject("Msxml2.XMLHTTP.6.0"); },
function() { return new ActiveXObject("Msxml2.XMLHTTP.3.0"); },
function() { return new ActiveXObject("Microsoft.XMLHTTP"); }
];
for (var i = 0, len = factories.length; i < len; ++i) {
try {
if ( factories[i]() ) {
return factories[i];
}
}
catch (e) {}
}
})();
var xmlHttp = createXmlHttpRequest();
xmlHttp.onreadystatechange = function() {
if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
readXML(xmlHttp.responseXML);
}
};
xmlHttp.open("GET", url, true);
xmlHttp.send(null);
I 'm having some trouble with my javascript code calling my php. Does anyone see an error in the following code? I swear I'm using code just like this on another part of the site...
var xmlHttp = createXmlHttpRequestObject();
var favSongArray = [];
function createXmlHttpRequestObject(){
var xmlHttp;
try{
xmlHttp = new XMLHttpRequest();
}
catch(e){
var XmlHttpVersions = new Array("MSXML2.XMLHTTP.6.0",
"MSXML2.XMLHTTP.5.0",
"MSXML2.XMLHTTP.4.0",
"MSXML2.XMLHTTP.3.0",
"MSXML2.XMLHTTP",
"Microsoft.XMLHTTP");
for(var i = 0; i < XmlHttpVersions.length && !xmlHttp; i++){
try{
xmlHttp = new ActiveXObject(XmlHttpVersions[i]);
}
catch(e){}
}
}
if(!xmlHttp){
alert("Error creating the XMLHttpRequest object.");
}
else{
return xmlHttp;
}
}
function process(){
if(xmlHttp){
alert("sever is available");
//if yes try
try{
xmlHttp.open("GET", "php/getUntimed.php", true);
xmlHttp.onreadystatechange = function(){handleRequestStateChange();};
alert("attempted to call p_handleRequestStateChange_test");
xmlHttp.send(null);
}//end try
catch(e){
alert("Can't connect to server: \n" + e.toString());
}//end catch
}//end if xmlHHttp
}//end function
function handleRequestStateChange(){
if(xmlHttp.readyState == 4){
if(xmlHttp.status == 200){
try{
u_handleServerResponse();
}//end try
catch(e){
alert("Error reading the response: " +e.toString());
}//end catch
}//end if
else{
alert("There was a problem retriving the data:\n" + xmlHttp.statusText);
}//end else
}//end if
}//end function
function u_handleServerResponse(){
//need to clear array each time
var response = xmlHttp.responseText;
favSongArray = response.split("+");
alert("made it here");
//getFlashMovie("trackTimer").trackTimer(favSongArray[0]);
}
process() is called from an onSubmit trigger. I keep getting a xmlHttp.status of zero. Does that make sense to anyone? Thanks
status == 0 usually means it was aborted -- either by pressing ESC or by changing the current address.
Or, since you're using a global xmlHttp, you may be calling open and/or send before the last request has had time to finish. Not entirely sure which, but one of them starts by calling abort.
Just navigate here.
http://docs.jquery.com/Ajax
Simple Example:
$.get('MyUrl.aspx', 'MyId=' + id, function(data){
$(data).appendTo($('#MyDiv'));
});
As Jonathan Lonowski says, status == 0 means aborted, and you said you execute that script onsubmit which would trigger the form to submit, thus reload the page and aborting the Ajax request. Take a look here too.
Why don't you try using ajax frameworks? Like jQuery for example.