I call ajax request in a loop. Around 20 of them. But few are getting aborted. How can I avoid that ?
Most of them are getting aborted.
function callURLAsync(url)
{
var xmlHttpReq = false;
var self = this;
// Mozilla/Safari
if (window.XMLHttpRequest)
{
self.xmlHttpReq = new XMLHttpRequest();
}
// IE
else if (window.ActiveXObject)
{
self.xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
}
self.xmlHttpReq.open('POST', url, true);
self.xmlHttpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
self.xmlHttpReq.onreadystatechange = function()
{
if (self.xmlHttpReq.readyState == 4) {
}
}
self.xmlHttpReq.send();
}
function startLogout(){
for(var i=0;i< 20;i++){
callURLAsync("myDummyURl");
}
}
Thanks
Sailesh
Reasons for Ajax calls to get aborted:
Form or page navigation - cancel the action that is causing navigation, you can not cancel or delay onunload
Calling abort
Reusing same XMLHttpRequest object
In your case it sounds like the button is navigating the page away. What you need to do is use event.preventDefault() or return false from the button click. After all the Ajax calls are done, you can use window.location to do the redirection.
Related
I am facing problem with my code in FireFox and Safari as below:
xhr = new window['XMLHttpRequest'];
xhr.onreadystatechange = function() {
if (done || xhr.readyState != 4) {
return;
}
done = true;
handleResponse(xhr.responseText, callback);
};
}
xhr.open('GET', uri+params, true);
xhr.withCredentials = true;
xhr.send(null);
function handleResponse(responseText, callback) {
var error;
var result;
try {
result = toucan.JSON.parse(responseText)['result']; //connectedAuth
logout result.
} catch (ex) {
result = undefined;
}
console.log("Result is" + result);
if (!result) {
var errorCode = 'UnknownError';
var errorMessage = 'An unknown error ocurred';
error = toucan.Base.format('%s: %s', errorCode, errorMessage);
}
invokeCallback(error, callback);
}
This is followed by redirection as :window.location.href = "index.php?module=login&method=logout";
However, I am not getting any response back from the request I made if it is followed by redirection in FireFox.
This works fine in Chrome but not in Firefox and is specific to the case when request is followed by redirection.
I do not have control on redirection code to be changed. Is there a way that the browser can be enforced to first complete the request and get the response before going for redirection while keeping the call asynchronous.
I would suggest you to use a promise, first create a function that run the ajax call that return the response from your server:
ajax_AuthUser(id,pass){
return $.ajax({
method: "POST",
url: "authUser.php",
data: { id: id, pass: pass}
})
}
Second use a done statement:
ajax_AuthUser(id,pass)
.done(function(response){
//check the response here !! maybe validate the json ?
var auth = JSON.parse(response)
if(auth.response == "approved"){
//do something here
}else{
//do other stuff here
}
}).fail(function(response){
//do something if fail
}).always(function(){
//do something after the call finished
})
If you want a live example here is a jsfiddle that show how promises work
Hope it helps
The data on the webpage is displayed dynamically and it seems that checking for every change in the html and extracting the data is a very daunting task and also needs me to use very unreliable XPaths. So I would want to be able to extract the data from the XHR packets.
I hope to be able to extract information from XHR packets as well as generate 'XHR' packets to be sent to the server.
The extracting information part is more important for me because the sending of information can be handled easily by automatically triggering html elements using casperjs.
I'm attaching a screenshot of what I mean.
The text in the response tab is the data I need to process afterwards. (This XHR response has been received from the server.)
This is not easily possible, because the resource.received event handler only provides meta data like url, headers or status, but not the actual data. The underlying phantomjs event handler acts the same way.
Stateless AJAX Request
If the ajax call is stateless, you may repeat the request
casper.on("resource.received", function(resource){
// somehow identify this request, here: if it contains ".json"
// it also also only does something when the stage is "end" otherwise this would be executed two times
if (resource.url.indexOf(".json") != -1 && resource.stage == "end") {
var data = casper.evaluate(function(url){
// synchronous GET request
return __utils__.sendAJAX(url, "GET");
}, resource.url);
// do something with data, you might need to JSON.parse(data)
}
});
casper.start(url); // your script
You may want to add the event listener to resource.requested. That way you don't need to way for the call to complete.
You can also do this right inside of the control flow like this (source: A: CasperJS waitForResource: how to get the resource i've waited for):
casper.start(url);
var res, resData;
casper.waitForResource(function check(resource){
res = resource;
return resource.url.indexOf(".json") != -1;
}, function then(){
resData = casper.evaluate(function(url){
// synchronous GET request
return __utils__.sendAJAX(url, "GET");
}, res.url);
// do something with the data here or in a later step
});
casper.run();
Stateful AJAX Request
If it is not stateless, you would need to replace the implementation of XMLHttpRequest. You will need to inject your own implementation of the onreadystatechange handler, collect the information in the page window object and later collect it in another evaluate call.
You may want to look at the XHR faker in sinon.js or use the following complete proxy for XMLHttpRequest (I modeled it after method 3 from How can I create a XMLHttpRequest wrapper/proxy?):
function replaceXHR(){
(function(window, debug){
function args(a){
var s = "";
for(var i = 0; i < a.length; i++) {
s += "\t\n[" + i + "] => " + a[i];
}
return s;
}
var _XMLHttpRequest = window.XMLHttpRequest;
window.XMLHttpRequest = function() {
this.xhr = new _XMLHttpRequest();
}
// proxy ALL methods/properties
var methods = [
"open",
"abort",
"setRequestHeader",
"send",
"addEventListener",
"removeEventListener",
"getResponseHeader",
"getAllResponseHeaders",
"dispatchEvent",
"overrideMimeType"
];
methods.forEach(function(method){
window.XMLHttpRequest.prototype[method] = function() {
if (debug) console.log("ARGUMENTS", method, args(arguments));
if (method == "open") {
this._url = arguments[1];
}
return this.xhr[method].apply(this.xhr, arguments);
}
});
// proxy change event handler
Object.defineProperty(window.XMLHttpRequest.prototype, "onreadystatechange", {
get: function(){
// this will probably never called
return this.xhr.onreadystatechange;
},
set: function(onreadystatechange){
var that = this.xhr;
var realThis = this;
that.onreadystatechange = function(){
// request is fully loaded
if (that.readyState == 4) {
if (debug) console.log("RESPONSE RECEIVED:", typeof that.responseText == "string" ? that.responseText.length : "none");
// there is a response and filter execution based on url
if (that.responseText && realThis._url.indexOf("whatever") != -1) {
window.myAwesomeResponse = that.responseText;
}
}
onreadystatechange.call(that);
};
}
});
var otherscalars = [
"onabort",
"onerror",
"onload",
"onloadstart",
"onloadend",
"onprogress",
"readyState",
"responseText",
"responseType",
"responseXML",
"status",
"statusText",
"upload",
"withCredentials",
"DONE",
"UNSENT",
"HEADERS_RECEIVED",
"LOADING",
"OPENED"
];
otherscalars.forEach(function(scalar){
Object.defineProperty(window.XMLHttpRequest.prototype, scalar, {
get: function(){
return this.xhr[scalar];
},
set: function(obj){
this.xhr[scalar] = obj;
}
});
});
})(window, false);
}
If you want to capture the AJAX calls from the very beginning, you need to add this to one of the first event handlers
casper.on("page.initialized", function(resource){
this.evaluate(replaceXHR);
});
or evaluate(replaceXHR) when you need it.
The control flow would look like this:
function replaceXHR(){ /* from above*/ }
casper.start(yourUrl, function(){
this.evaluate(replaceXHR);
});
function getAwesomeResponse(){
return this.evaluate(function(){
return window.myAwesomeResponse;
});
}
// stops waiting if window.myAwesomeResponse is something that evaluates to true
casper.waitFor(getAwesomeResponse, function then(){
var data = JSON.parse(getAwesomeResponse());
// Do something with data
});
casper.run();
As described above, I create a proxy for XMLHttpRequest so that every time it is used on the page, I can do something with it. The page that you scrape uses the xhr.onreadystatechange callback to receive data. The proxying is done by defining a specific setter function which writes the received data to window.myAwesomeResponse in the page context. The only thing you need to do is retrieving this text.
JSONP Request
Writing a proxy for JSONP is even easier, if you know the prefix (the function to call with the loaded JSON e.g. insert({"data":["Some", "JSON", "here"],"id":"asdasda")). You can overwrite insert in the page context
after the page is loaded
casper.start(url).then(function(){
this.evaluate(function(){
var oldInsert = insert;
insert = function(json){
window.myAwesomeResponse = json;
oldInsert.apply(window, arguments);
};
});
}).waitFor(getAwesomeResponse, function then(){
var data = JSON.parse(getAwesomeResponse());
// Do something with data
}).run();
or before the request is received (if the function is registered just before the request is invoked)
casper.on("resource.requested", function(resource){
// filter on the correct call
if (resource.url.indexOf(".jsonp") != -1) {
this.evaluate(function(){
var oldInsert = insert;
insert = function(json){
window.myAwesomeResponse = json;
oldInsert.apply(window, arguments);
};
});
}
}).run();
casper.start(url).waitFor(getAwesomeResponse, function then(){
var data = JSON.parse(getAwesomeResponse());
// Do something with data
}).run();
I may be late into the party, but the answer may help someone like me who would fall into this problem later in future.
I had to start with PhantomJS, then moved to CasperJS but finally settled with SlimerJS. Slimer is based on Phantom, is compatible with Casper, and can send you back the response body using the same onResponseReceived method, in "response.body" part.
Reference: https://docs.slimerjs.org/current/api/webpage.html#webpage-onresourcereceived
#Artjom's answer's doesn't work for me in the recent Chrome and CasperJS versions.
Based on #Artjom's answer and based on gilly3's answer on how to replace XMLHttpRequest, I have composed a new solution that should work in most/all versions of the different browsers. Works for me.
SlimerJS cannot work on newer version of FireFox, therefore no good for me.
Here is the the generic code to add a listner to load of XHR (not dependent on CasperJS):
var addXHRListener = function (XHROnStateChange) {
var XHROnLoad = function () {
if (this.readyState == 4) {
XHROnStateChange(this)
}
}
var open_original = XMLHttpRequest.prototype.open;
XMLHttpRequest.prototype.open = function (method, url, async, unk1, unk2) {
this.requestUrl = url
open_original.apply(this, arguments);
};
var xhrSend = XMLHttpRequest.prototype.send;
XMLHttpRequest.prototype.send = function () {
var xhr = this;
if (xhr.addEventListener) {
xhr.removeEventListener("readystatechange", XHROnLoad);
xhr.addEventListener("readystatechange", XHROnLoad, false);
} else {
function readyStateChange() {
if (handler) {
if (handler.handleEvent) {
handler.handleEvent.apply(xhr, arguments);
} else {
handler.apply(xhr, arguments);
}
}
XHROnLoad.apply(xhr, arguments);
setReadyStateChange();
}
function setReadyStateChange() {
setTimeout(function () {
if (xhr.onreadystatechange != readyStateChange) {
handler = xhr.onreadystatechange;
xhr.onreadystatechange = readyStateChange;
}
}, 1);
}
var handler;
setReadyStateChange();
}
xhrSend.apply(xhr, arguments);
};
}
Here is CasperJS code to emit a custom event on load of XHR:
casper.on("page.initialized", function (resource) {
var emitXHRLoad = function (xhr) {
window.callPhantom({eventName: 'xhr.load', eventData: xhr})
}
this.evaluate(addXHRListener, emitXHRLoad);
});
casper.on('remote.callback', function (data) {
casper.emit(data.eventName, data.eventData)
});
Here is a code to listen to "xhr.load" event and get the XHR response body:
casper.on('xhr.load', function (xhr) {
console.log('xhr load', xhr.requestUrl)
console.log('xhr load', xhr.responseText)
});
Additionally, you can also directly download the content and manipulate it later.
Here is the example of the script I am using to retrieve a JSON and save it locally :
var casper = require('casper').create({
pageSettings: {
webSecurityEnabled: false
}
});
var url = 'https://twitter.com/users/username_available?username=whatever';
casper.start('about:blank', function() {
this.download(url, "hop.json");
});
casper.run(function() {
this.echo('Done.').exit();
});
Hi I can see this has been discussed but after perusing the issues/answers I still don't seem to be able to get even this simple AJAX call to bump out of ready state 1.
Here's the Javascript I have:
<script language="javascript" type="text/javascript">
var request;
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!");
}
function loadClassesBySchool()
{
//get require web form pieces for this call
createRequest(); // function to get xmlhttp object
var schoolId = getDDLSelectionValue("ddlSchools");
var grade = getDDLSelectionValue("ddlGrades");
var url = "courses.php?grades=" + escape(grade) + "&schoolId=" + escape(schoolId);
//open server connection
request.open("GET", url, true);
//Setup callback function for server response
//+++read on overflow that some fixed the issue with an onload event this simply had
//+++the handle spitback 2 readystate = 1 alerts
request.onload = updateCourses();
request.onreadystatechanged = updateCourses();
//send the result
request.send();
}
function updateCourses()
{
alert('ready state changed' + request.readyState);
}
function getDDLSelectionValue(ddlID)
{
return document.getElementById(ddlID).options[document.getElementById(ddlID).selectedIndex].value;
}
</script>
The PHP is HERE just a simple print which if i navigate to in the browser (IE/Chrome) loads fine:
<?php
print "test";
?>
I'm quite new at this but seems like I can't get the most bare bones AJAX calls to work, any help as to how work past this would be greatly appreciated.
All I get out of my callback function 'updateCourses' is a 1...
Well after more digging I actually gave up and switched over to jQuery which should for all intents and purposes be doing the EXACT same thing except for the fact that jQuery works... I was just less comfortable with it but so be it.
Here's the jQuery to accomplish the same:
function loadCoursesBySchool(){
var grades = getDDLSelectionValue("ddlGrades");
var schoolId = getDDLSelectionValue("ddlSchools");
jQuery.ajax({
url: "courses.php?grades=" + grades + "&schoolId=" + schoolId,
success: function (data) {
courseDisplay(data);
}
});
}
function courseDisplay(response)
{
//check if anything was setn back!?
if(!response)
{
$("#ddlCourses").html("");
//do nothing?
}
else
{
//empty DLL
$("#ddlCourses").html("");
//add entries
$(response).appendTo("#ddlCourses");
}
}
I've an AJAX request which will be made every 5 seconds. But the problem is before the AJAX request if the previous request is not completed I've to abort that request and make a new request.
My code is something like this, how to resolve this issue?
$(document).ready(
var fn = function(){
$.ajax({
url: 'ajax/progress.ftl',
success: function(data) {
//do something
}
});
};
var interval = setInterval(fn, 500);
);
The jquery ajax method returns a XMLHttpRequest object. You can use this object to cancel the request.
The XMLHttpRequest has a abort method, which cancels the request, but if the request has already been sent to the server then the server will process the request even if we abort the request but the client will not wait for/handle the response.
The xhr object also contains a readyState which contains the state of the request(UNSENT-0, OPENED-1, HEADERS_RECEIVED-2, LOADING-3 and DONE-4). we can use this to check whether the previous request was completed.
$(document).ready(
var xhr;
var fn = function(){
if(xhr && xhr.readyState != 4){
xhr.abort();
}
xhr = $.ajax({
url: 'ajax/progress.ftl',
success: function(data) {
//do something
}
});
};
var interval = setInterval(fn, 500);
);
When you make a request to a server, have it check to see if a progress is not null (or fetching that data) first. If it is fetching data, abort the previous request and initiate the new one.
var progress = null
function fn () {
if (progress) {
progress.abort();
}
progress = $.ajax('ajax/progress.ftl', {
success: function(data) {
//do something
progress = null;
}
});
}
I know this might be a little late but i experience similar issues where calling the abort method didnt really aborted the request. instead the browser was still waiting for a response that it never uses.
this code resolved that issue.
try {
xhr.onreadystatechange = null;
xhr.abort();
} catch (e) {}
Why should you abort the request?
If each request takes more than five seconds, what will happen?
You shouldn't abort the request if the parameter passing with the request is not changing.
eg:- the request is for retrieving the notification data.
In such situations, The nice approach is that set a new request only after completing the previous Ajax request.
$(document).ready(
var fn = function(){
$.ajax({
url: 'ajax/progress.ftl',
success: function(data) {
//do something
},
complete: function(){setTimeout(fn, 500);}
});
};
var interval = setTimeout(fn, 500);
);
jQuery:
Use this as a starting point - as inspiration.
I solved it like this:
(this is not a perfect solution, it just aborts the last instance and is WIP code)
var singleAjax = function singleAjax_constructor(url, params) {
// remember last jQuery's get request
if (this.lastInstance) {
this.lastInstance.abort(); // triggers .always() and .fail()
this.lastInstance = false;
}
// how to use Deferred : http://api.jquery.com/category/deferred-object/
var $def = new $.Deferred();
// pass the deferrer's request handlers into the get response handlers
this.lastInstance = $.get(url, params)
.fail($def.reject) // triggers .always() and .fail()
.success($def.resolve); // triggers .always() and .done()
// return the deferrer's "control object", the promise object
return $def.promise();
}
// initiate first call
singleAjax('/ajax.php', {a: 1, b: 2})
.always(function(a,b,c) {console && console.log(a,b,c);});
// second call kills first one
singleAjax('/ajax.php', {a: 1, b: 2})
.always(function(a,b,c) {console && console.log(a,b,c);});
// here you might use .always() .fail() .success() etc.
You can use jquery-validate.js . The following is the code snippet from jquery-validate.js.
// ajax mode: abort
// usage: $.ajax({ mode: "abort"[, port: "uniqueport"]});
// if mode:"abort" is used, the previous request on that port (port can be undefined) is aborted via XMLHttpRequest.abort()
var pendingRequests = {},
ajax;
// Use a prefilter if available (1.5+)
if ( $.ajaxPrefilter ) {
$.ajaxPrefilter(function( settings, _, xhr ) {
var port = settings.port;
if ( settings.mode === "abort" ) {
if ( pendingRequests[port] ) {
pendingRequests[port].abort();
}
pendingRequests[port] = xhr;
}
});
} else {
// Proxy ajax
ajax = $.ajax;
$.ajax = function( settings ) {
var mode = ( "mode" in settings ? settings : $.ajaxSettings ).mode,
port = ( "port" in settings ? settings : $.ajaxSettings ).port;
if ( mode === "abort" ) {
if ( pendingRequests[port] ) {
pendingRequests[port].abort();
}
pendingRequests[port] = ajax.apply(this, arguments);
return pendingRequests[port];
}
return ajax.apply(this, arguments);
};
}
So that you just only need to set the parameter mode to abort when you are making ajax request.
Ref:https://cdnjs.cloudflare.com/ajax/libs/jquery-validate/1.14.0/jquery.validate.js
Create a function to call your API. Within this function we define request callApiRequest = $.get(... - even though this is a definition of a variable, the request is called immediately, but now we have the request defined as a variable. Before the request is called, we check if our variable is defined typeof(callApiRequest) != 'undefined' and also if it is pending suggestCategoryRequest.state() == 'pending' - if both are true, we .abort() the request which will prevent the success callback from running.
// We need to wrap the call in a function
callApi = function () {
//check if request is defined, and status pending
if (typeof(callApiRequest) != 'undefined'
&& suggestCategoryRequest.state() == 'pending') {
//abort request
callApiRequest.abort()
}
//define and make request
callApiRequest = $.get("https://example.com", function (data) {
data = JSON.parse(data); //optional (for JSON data format)
//success callback
});
}
Your server/API might not support aborting the request (what if API executed some code already?), but the javascript callback will not fire. This is useful, when for example you are providing input suggestions to a user, such as hashtags input.
You can further extend this function by adding definition of error callback - what should happen if request was aborted.
Common use-case for this snippet would be a text input that fires on keypress event. You can use a timeout, to prevent sending (some of) requests that you will have to cancel .abort().
You should also check for readyState 0. Because when you use xhr.abort() this function set readyState to 0 in this object, and your if check will be always true - readyState !=4
$(document).ready(
var xhr;
var fn = function(){
if(xhr && xhr.readyState != 4 && xhr.readyState != 0){
xhr.abort();
}
xhr = $.ajax({
url: 'ajax/progress.ftl',
success: function(data) {
//do something
}
});
};
var interval = setInterval(fn, 500);
);
$(document).ready(function() {
function ajaxselectrss(rssurlvar) {
var ajaxRequest; // The variable that makes Ajax possible!
try{
// Opera 8.0+, Firefox, Safari
ajaxRequest = new XMLHttpRequest();
} catch (e){
// Internet Explorer Browsers
try{
ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try{
ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e){
// Something went wrong
alert("Your browser broke!");
return false;
}
}
}
// Create a function that will receive data sent from the server
ajaxRequest.onreadystatechange = function(){
if(ajaxRequest.readyState == 4){
var ajaxDisplay = document.getElementById('news');
ajaxDisplay.innerHTML = ajaxRequest.responseText;
}
}
//var rssurlvar = $(this).attr("title");
var queryString = "rurl=" + rssurlvar;
var urltofile = "rssget.php";
ajaxRequest.open("POST", urltofile, true);
ajaxRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
ajaxRequest.setRequestHeader("Content-length", queryString.length);
ajaxRequest.setRequestHeader("Connection", "close");
ajaxRequest.send(queryString);
}
$(".rshownews").click(function() {
window.setInterval(function() {ajaxselectrss($(this).attr("title"))}, 1000);
});
});
The POST query is "undefined" (Firebug).
You should use $.ajax - it will standardise the whole XmlHTTPRequest thing across browsers.
$.ajax({
type: "POST",
url: "rssget.php",
data: queryString,
success: function(data) {
$('#news').html(data);
}
});
(And, BTW, if you setInterval in your click handler, you will start a new periodic call to your ajaxselectrss function every time the button is clicked.)
Also, your context has changed due to the wrapper function. Try changing your click handler like so:
$(".rshownews").click(function() {
var _this = this;
window.setInterval(function() {ajaxselectrss($(_this).attr("title"))}, 1000);
});
Since you seem to use jquery anyway ($(document).ready) you could use it's wrapper for simplifying ajax-requests.
http://api.jquery.com/jQuery.post