I have a JavaScript widget which provides standard extension points. One of them is the beforecreate function. It should return false to prevent an item from being created.
I've added an Ajax call into this function using jQuery:
beforecreate: function (node, targetNode, type, to) {
jQuery.get('http://example.com/catalog/create/' + targetNode.id + '?name=' + encode(to.inp[0].value),
function (result) {
if (result.isOk == false)
alert(result.message);
});
}
But I want to prevent my widget from creating the item, so I should return false in the mother-function, not in the callback. Is there a way to perform a synchronous AJAX request using jQuery or any other in-browser API?
From the jQuery documentation: you specify the asynchronous option to be false to get a synchronous Ajax request. Then your callback can set some data before your mother function proceeds.
Here's what your code would look like if changed as suggested:
beforecreate: function (node, targetNode, type, to) {
jQuery.ajax({
url: 'http://example.com/catalog/create/' + targetNode.id + '?name=' + encode(to.inp[0].value),
success: function (result) {
if (result.isOk == false) alert(result.message);
},
async: false
});
}
You can put the jQuery's Ajax setup in synchronous mode by calling
jQuery.ajaxSetup({async:false});
And then perform your Ajax calls using jQuery.get( ... );
Then just turning it on again once
jQuery.ajaxSetup({async:true});
I guess it works out the same thing as suggested by #Adam, but it might be helpful to someone that does want to reconfigure their jQuery.get() or jQuery.post() to the more elaborate jQuery.ajax() syntax.
Excellent solution! I noticed when I tried to implement it that if I returned a value in the success clause, it came back as undefined. I had to store it in a variable and return that variable. This is the method I came up with:
function getWhatever() {
// strUrl is whatever URL you need to call
var strUrl = "", strReturn = "";
jQuery.ajax({
url: strUrl,
success: function(html) {
strReturn = html;
},
async:false
});
return strReturn;
}
All of these answers miss the point that doing an Ajax call with async:false will cause the browser to hang until the Ajax request completes. Using a flow control library will solve this problem without hanging up the browser. Here is an example with Frame.js:
beforecreate: function(node,targetNode,type,to) {
Frame(function(next)){
jQuery.get('http://example.com/catalog/create/', next);
});
Frame(function(next, response)){
alert(response);
next();
});
Frame.init();
}
function getURL(url){
return $.ajax({
type: "GET",
url: url,
cache: false,
async: false
}).responseText;
}
//example use
var msg=getURL("message.php");
alert(msg);
Keep in mind that if you're doing a cross-domain Ajax call (by using JSONP) - you can't do it synchronously, the async flag will be ignored by jQuery.
$.ajax({
url: "testserver.php",
dataType: 'jsonp', // jsonp
async: false //IGNORED!!
});
For JSONP-calls you could use:
Ajax-call to your own domain - and do the cross-domain call server-side
Change your code to work asynchronously
Use a "function sequencer" library like Frame.js (this answer)
Block the UI instead of blocking the execution (this answer) (my favourite way)
Note: You shouldn't use async: false due to this warning messages:
Starting with Gecko 30.0 (Firefox 30.0 / Thunderbird 30.0 / SeaMonkey 2.27), synchronous requests on the main thread have been deprecated due to the negative effects to the user experience.
Chrome even warns about this in the console:
Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.
This could break your page if you are doing something like this since it could stop working any day.
If you want to do it a way that still feels like if it's synchronous but still don't block then you should use async/await and probably also some ajax that is based on promises like the new Fetch API
async function foo() {
var res = await fetch(url)
console.log(res.ok)
var json = await res.json()
console.log(json)
}
Edit
chrome is working on Disallowing sync XHR in page dismissal when the page is being navigated away or closed by the user. This involves beforeunload, unload, pagehide and visibilitychange.
if this is your use case then you might want to have a look at navigator.sendBeacon instead
It is also possible for the page to disable sync req with either http headers or iframe's allow attribute
I used the answer given by Carcione and modified it to use JSON.
function getUrlJsonSync(url){
var jqxhr = $.ajax({
type: "GET",
url: url,
dataType: 'json',
cache: false,
async: false
});
// 'async' has to be 'false' for this to work
var response = {valid: jqxhr.statusText, data: jqxhr.responseJSON};
return response;
}
function testGetUrlJsonSync()
{
var reply = getUrlJsonSync("myurl");
if (reply.valid == 'OK')
{
console.dir(reply.data);
}
else
{
alert('not valid');
}
}
I added the dataType of 'JSON' and changed the .responseText to responseJSON.
I also retrieved the status using the statusText property of the returned object. Note, that this is the status of the Ajax response, not whether the JSON is valid.
The back-end has to return the response in correct (well-formed) JSON, otherwise the returned object will be undefined.
There are two aspects to consider when answering the original question. One is telling Ajax to perform synchronously (by setting async: false) and the other is returning the response via the calling function's return statement, rather than into a callback function.
I also tried it with POST and it worked.
I changed the GET to POST and added data: postdata
function postUrlJsonSync(url, postdata){
var jqxhr = $.ajax({
type: "POST",
url: url,
data: postdata,
dataType: 'json',
cache: false,
async: false
});
// 'async' has to be 'false' for this to work
var response = {valid: jqxhr.statusText, data: jqxhr.responseJSON};
return response;
}
Note that the above code only works in the case where async is false. If you were to set async: true the returned object jqxhr would not be valid at the time the AJAX call returns, only later when the asynchronous call has finished, but that is much too late to set the response variable.
With async: false you get yourself a blocked browser.
For a non blocking synchronous solution you can use the following:
ES6/ECMAScript2015
With ES6 you can use a generator & the co library:
beforecreate: function (node, targetNode, type, to) {
co(function*(){
let result = yield jQuery.get('http://example.com/catalog/create/' + targetNode.id + '?name=' + encode(to.inp[0].value));
//Just use the result here
});
}
ES7
With ES7 you can just use asyc await:
beforecreate: function (node, targetNode, type, to) {
(async function(){
let result = await jQuery.get('http://example.com/catalog/create/' + targetNode.id + '?name=' + encode(to.inp[0].value));
//Just use the result here
})();
}
This is example:
$.ajax({
url: "test.html",
async: false
}).done(function(data) {
// Todo something..
}).fail(function(xhr) {
// Todo something..
});
Firstly we should understand when we use $.ajax and when we use $.get/$.post
When we require low level control over the ajax request such as request header settings, caching settings, synchronous settings etc.then we should go for $.ajax.
$.get/$.post: When we do not require low level control over the ajax request.Only simple get/post the data to the server.It is shorthand of
$.ajax({
url: url,
data: data,
success: success,
dataType: dataType
});
and hence we can not use other features(sync,cache etc.) with $.get/$.post.
Hence for low level control(sync,cache,etc.) over ajax request,we should go for $.ajax
$.ajax({
type: 'GET',
url: url,
data: data,
success: success,
dataType: dataType,
async:false
});
this is my simple implementation for ASYNC requests with jQuery. I hope this help anyone.
var queueUrlsForRemove = [
'http://dev-myurl.com/image/1',
'http://dev-myurl.com/image/2',
'http://dev-myurl.com/image/3',
];
var queueImagesDelete = function(){
deleteImage( queueUrlsForRemove.splice(0,1), function(){
if (queueUrlsForRemove.length > 0) {
queueImagesDelete();
}
});
}
var deleteImage = function(url, callback) {
$.ajax({
url: url,
method: 'DELETE'
}).done(function(response){
typeof(callback) == 'function' ? callback(response) : null;
});
}
queueImagesDelete();
Because XMLHttpReponse synchronous operation is deprecated I came up with the following solution that wraps XMLHttpRequest. This allows ordered AJAX queries while still being asycnronous in nature, which is very useful for single use CSRF tokens.
It is also transparent so libraries such as jQuery will operate seamlessly.
/* wrap XMLHttpRequest for synchronous operation */
var XHRQueue = [];
var _XMLHttpRequest = XMLHttpRequest;
XMLHttpRequest = function()
{
var xhr = new _XMLHttpRequest();
var _send = xhr.send;
xhr.send = function()
{
/* queue the request, and if it's the first, process it */
XHRQueue.push([this, arguments]);
if (XHRQueue.length == 1)
this.processQueue();
};
xhr.processQueue = function()
{
var call = XHRQueue[0];
var xhr = call[0];
var args = call[1];
/* you could also set a CSRF token header here */
/* send the request */
_send.apply(xhr, args);
};
xhr.addEventListener('load', function(e)
{
/* you could also retrieve a CSRF token header here */
/* remove the completed request and if there is more, trigger the next */
XHRQueue.shift();
if (XHRQueue.length)
this.processQueue();
});
return xhr;
};
Since the original question was about jQuery.get, it is worth mentioning here that (as mentioned here) one could use async: false in a $.get() but ideally avoid it since asynchronous XMLHTTPRequest is deprecated (and the browser may give a warning):
$.get({
url: url,// mandatory
data: data,
success: success,
dataType: dataType,
async:false // to make it synchronous
});
Related
I have a general ajax function which I'm calling from loads of places in my code. It's pretty standard except for some extra debugging stuff I've recently added (to try to solve this issue), with a global 'ajaxworking' variable:
rideData.myAjax = function (url, type, data, successfunc) {
var dataJson = JSON.stringify(data),
thisurl = quilkinUrlBase() + url;
if (ajaxworking.length > 0) {
console.log(thisurl + ": concurrent Ajax call with: " + ajaxworking);
}
ajaxworking = thisurl;
$.ajax({
type: type,
data: dataJson,
url: thisurl,
contentType: "application/json; charset=utf-8",
dataType: "json",
async: true,
success: function (response) {
ajaxworking = '';
successfunc(response);
},
error: webRequestFailed
});
};
Now, there's one section of my code where a second ajax call is made depending on the result of the first:
getWebRides = function (date) {
var rideIDs = [];
var intdays = bleTime.toIntDays(date);
rideData.myAjax("GetRidesForDate", "POST", intdays, function (response) {
rides = response;
if (rides.length === 0) {
$('#ridelist').empty(); // this will also remove any handlers
qPopup.Alert("No rides found for " + bleTime.DateString(date));
return null;
}
$.each(rides, function (index) {
rideIDs.push(rides[index].rideID);
});
GetParticipants(rideIDs);
});
},
'GetParticipants' (which also calls 'myAjax') works fine - most of the time. But in another part of my code, 'GetWebRides' is itself called directly after another ajax call - i.e. there are 3 calls, each successive one depending on the previous. The 'top-level' call is as follows:
rideData.myAjax("SaveRide", "POST", ride, function (response) {
// if successful, response should be just a new ID
if (response.length < 5) {
// document re-arrangement code snipped here for brevity
getWebRides(date);
}
else {
qPopup.Alert(response);
}
});
so, only when there are three successive calls like this, I'm getting the 'concurrent' catch in the third one:
GetParticipants: concurrent call with GetRidesForDate
and (if allowed to proceed) this causes a nasty probem at the server with datareaders already being open. But why is this only occurring when GetParticipants is called as the third in the chain?
I see, after some research. that there are now other ways of arranging async calls, e.g. using 'Promises', but I'd like to understand what's going on here.
Solved this.
Part of the 'document re-arrangement code' that I had commented out for this post, was in fact calling another Ajax call indirectly (very indirectly, hence it took a long time to find).
i have small issue with exchanging data in between methods in a JavaScript object (class):
var TEST = (function () {
var TEST = function() {
};
TEST.prototype.get = function() {
$.ajax({
type: "GET",
url: "http://test.com/getall",
dataType: "json",
success: function (data) {
return data; // if i console log this i will get a json obj
}
});
};
TEST.prototype.parse = function(data) {
$.each(this.get(), function(k, v){
console.log(v);
});
};
return TEST;
})();
so i am trying to call one method in the each statement in another method. the issue is that
the response is undefined.
i also tried it like this, but with he same result
var testing = new TEST();
var get = testing.get();
testing.parse(get);
What am i missing? how can i return the data from this.get to be used in this.parse.
thanks
$.ajax() per default is asynchronous. That means, that the execution of your function get() wont wait until the request is finished. Hence you return no value from it, which results in undefined being returned.
In order to have your get() function be able to return a value, you would have to do the request in a synchronous way and set a variable in the outer function (as success itself is just another function, whose return value is not caught):
TEST.prototype.get = function() {
var result;
$.ajax({
type: "GET",
url: "http://test.com/getall",
async: false, // this is the important part!
dataType: "json",
success: function (data) {
result = data;
}
});
return result;
};
EDIT
As mentioned by #pebbl, this will halt the execution of all your scripts, until the request is done. Hence your whole page will be blocked for the time being.
The general approach is to use callbacks in such cases, which will be executed once the requests finished. So in your case something like this:
TEST.prototype.get = function( cb ) {
$.ajax({
type: "GET",
url: "http://test.com/getall",
dataType: "json",
success: function (data) {
cb( data );
}
});
};
with later on calling like this:
var testing = new TEST();
testing.get( function( data ) {
testing.parse( data );
});
You can't construct your function this way as you are relying on an asyncronous call, which will return it's result outside of the normal execution flow. The only way you can actually receive the result of your .get function is to use a callback.
Put simply your value isn't being returned from the .get function, it's being returned from the callback you are passing into jQuery's .ajax method.
You'd be far better off redesigning your code so as to still support the asyncronous call -- rather than disabling async.
A rough idea is to change your parse function like so:
TEST.prototype.parse = function(data) {
this.get(function(result){
$.each(result, function(k, v){
console.log(v);
});
});
};
And to change your get function accordingly:
TEST.prototype.get = function(callback) {
$.ajax({
type: "GET",
url: "http://test.com/getall",
dataType: "json",
success: callback
});
};
The above is just a quick example, you'd be wise reading up on the following jQuery topics:
http://api.jquery.com/promise/
http://api.jquery.com/category/deferred-object/
If you design your code around the promise pattern you'll find it complicated at first, but it gives you a lot of power in your code -- and gets around the whole callback stacking madness you can end up with when dealing in ajax calls.
Whilst it's not entirely clear from the jQuery.ajax documentation, this function returns a jqXHR object which implements the promise interface. So this means you can use the promise methods done, always and fail.
http://api.jquery.com/jQuery.ajax/
I am completely new to Javascript/jquery world and need some help. Right now, I am writing one html page where I have to make 5 different Ajax calls to get the data to plot graphs. Right now, I am calling these 5 ajax calls like this:
$(document).ready(function() {
area0Obj = $.parseJSON($.ajax({
url : url0,
async : false,
dataType : 'json'
}).responseText);
area1Obj = $.parseJSON($.ajax({
url : url1,
async : false,
dataType : 'json'
}).responseText);
.
.
.
area4Obj = $.parseJSON($.ajax({
url : url4,
async : false,
dataType : 'json'
}).responseText);
// some code for generating graphs
)} // closing the document ready function
My problem is that in above scenario, all the ajax calls are going serially. That is, after 1 call is complete 2 starts, when 2 completes 3 starts and so on .. Each Ajax call is taking roughly around 5 - 6 sec to get the data, which makes the over all page to be loaded in around 30 sec.
I tried making the async type as true but in that case I dont get the data immediately to plot the graph which defeats my purpose.
My question is:
How can I make these calls parallel, so that I start getting all this data parallely and my page could be loaded in less time?
Thanks in advance.
Using jQuery.when (deferreds):
$.when( $.ajax("/req1"), $.ajax("/req2"), $.ajax("/req3") ).then(function(resp1, resp2, resp3){
// plot graph using data from resp1, resp2 & resp3
});
callback function only called when all 3 ajax calls are completed.
You can't do that using async: false - the code executes synchronously, as you already know (i.e. an operation won't start until the previous one has finished).
You will want to set async: true (or just omit it - by default it's true). Then define a callback function for each AJAX call. Inside each callback, add the received data to an array. Then, check whether all the data has been loaded (arrayOfJsonObjects.length == 5). If it has, call a function to do whatever you want with the data.
Let's try to do it in this way:
<script type="text/javascript" charset="utf-8">
$(document).ready(function() {
var area0Obj = {responseText:''};
var area1Obj = {responseText:''};
var area2Obj = {responseText:''};
var url0 = 'http://someurl/url0/';
var url1 = 'http://someurl/url1/';
var url2 = 'http://someurl/url2/';
var getData = function(someURL, place) {
$.ajax({
type : 'POST',
dataType : 'json',
url : someURL,
success : function(data) {
place.responseText = data;
console.log(place);
}
});
}
getData(url0, area0Obj);
getData(url1, area1Obj);
getData(url2, area2Obj);
});
</script>
if server side will be smth. like this:
public function url0() {
$answer = array(
array('smth' => 1, 'ope' => 'one'),
array('smth' => 8, 'ope' => 'two'),
array('smth' => 5, 'ope' => 'three')
);
die(json_encode($answer));
}
public function url1() {
$answer = array('one','two','three');
die(json_encode($answer));
}
public function url2() {
$answer = 'one ,two, three';
die(json_encode($answer));
}
So there, as you can see, created one function getData() for getting data from server and than it called 3 times. Results will be received in asynchronous way so, for example, first can get answer for third call and last for first call.
Console answer will be:
[{"smth":1,"ope":"one"},{"smth":8,"ope":"two"},{"smth":5,"ope":"three"}]
["one","two","three"]
"one ,two, three"
PS. please read this: http://api.jquery.com/jQuery.ajax/ there you can clearly see info about async. There default async param value = true.
By default, all requests are sent asynchronously (i.e. this is set to true by default). If you need synchronous requests, set this option to false. Cross-domain requests and dataType: "jsonp" requests do not support synchronous operation. Note that synchronous requests may temporarily lock the browser, disabling any actions while the request is active...
The following worked for me - I had multiple ajax calls with the need to pass a serialised object:
var args1 = {
"table": "users",
"order": " ORDER BY id DESC ",
"local_domain":""
}
var args2 = {
"table": "parts",
"order": " ORDER BY date DESC ",
"local_domain":""
}
$.when(
$.ajax({
url: args1.local_domain + '/my/restful',
headers: {
'Content-Type': 'application/x-www-form-urlencoded'
},
type: "POST",
dataType : "json",
contentType: "application/json; charset=utf-8",
data : JSON.stringify(args1),
error: function(err1) {
alert('(Call 1)An error just happened...' + JSON.stringify(err1));
}
}),
$.ajax({
url: args2.local_domain + '/my/restful',
headers: {
'Content-Type': 'application/x-www-form-urlencoded'
},
type: "POST",
dataType : "json",
contentType: "application/json; charset=utf-8",
data : JSON.stringify(args2),
error: function(err2) {
calert('(Call 2)An error just happened...' + JSON.stringify(err2));
}
})
).then(function( data1, data2 ) {
data1 = cleanDataString(data1);
data2 = cleanDataString(data2);
data1.forEach(function(e){
console.log("ids" + e.id)
});
data2.forEach(function(e){
console.log("dates" + e.date)
});
})
function cleanDataString(data){
data = decodeURIComponent(data);
// next if statement was only used because I got additional object on the back of my JSON object
// parsed it out while serialised and then added back closing 2 brackets
if(data !== undefined && data.toString().includes('}],success,')){
temp = data.toString().split('}],success,');
data = temp[0] + '}]';
}
data = JSON.parse(data);
return data; // return parsed object
}
In jQuery.ajax you should provide a callback method as below:
j.ajax({
url : url0,
async : true,
dataType : 'json',
success:function(data){
console.log(data);
}
}
or you can directly use
jQuery.getJSON(url0, function(data){
console.log(data);
});
reference
You won't be able to handle it like your example. Setting to async uses another thread to make the request on and lets your application continue.
In this case you should utilize a new function that will plot an area out, then use the callback functions of the ajax request to pass the data to that function.
For example:
$(document).ready(function() {
function plotArea(data, status, jqXHR) {
// access the graph object and apply the data.
var area_data = $.parseJSON(data);
}
$.ajax({
url : url0,
async : false,
dataType : 'json',
success: poltArea
});
$.ajax({
url : url1,
async : false,
dataType : 'json',
success: poltArea
});
$.ajax({
url : url4,
async : false,
dataType : 'json',
success: poltArea
});
// some code for generating graphs
}); // closing the document ready function
It looks like you need to dispatch your request asynchronously and define a callback function to get the response.
The way you did, it'll wait until the variable is successfully assigned (meaning: the response has just arrived) until it proceeds to dispatch the next request. Just use something like this.
$.ajax({
url: url,
dataType: 'json',
data: data,
success: function(data) {
area0Obj = data;
}
});
This should do the trick.
Here's a solution to your issue: http://jsfiddle.net/YZuD9/
you may combine all the functionality of the different ajax functions into 1 ajax function, or from 1 ajax function, call the other functions (they would be private/controller side in this case) and then return the result. Ajax calls do stall a bit, so minimizing them is the way to go.
you can also make the ajax functions asynchronous (which then would behave like normal functions), then you can render the graph at the end, after all the functions return their data.
I have a javascript function called GetRequest() that calls the server with $.ajax() and receives a json string:
function GetRequest(ThePage) {
RequestedPage = parseInt(ThePageNumber,10);
$.ajax({
type: "POST",
contentType: "application/json; charset=utf-8",
url: "../Pages/MyPage.aspx/GetPage",
data: "{'ThePage':'" + ThePageNumber + "'}",
dataType: "json",
success: function (msg) {
var data = msg.hasOwnProperty("d") ? msg.d : msg;
OnSucessCallBack(data);
},
error: function (xhr, status, error) {
alert(xhr.statusText);
}
});
};
I have a function called ShowData() that calls GetRequest() and must wait until GetRequest receives its data before continuing.
function ShowData() {
//some code that determines the page number
GetRequest(ThePageNumber);
//wait until the data is in
};
I use GetRequest in several places so I can't use its success function in the context of ShowData.
How do I make my function ShowData pause its execution until GetRequest is finished? I thought of changing the OnSuccessCallBack function and determine which function initially called GetRequest() but I'm not sure on how to best do this.
Thanks for your suggestions.
add a function pass-in to GetRequest like so:
function GetRequest(pageNumber, successCallback){
//I admit this isn't "elegant" but it's most assuredly readable
var callback;
if (successCallback == null) {
callback = //default callback definition here
} else {
callback = successCallback;
}
//do everything else the same here
//except use the callback defined above
}
This gives you the flexibility to add in a separate callback handler for the onsuccess
Alternately, do the same as above, but use the "onComplete" handler unless you need the data specifically on the return (it doesn't appear as tho you do).
I'm going to strenuously suggest that you do use callbacks for asynchronous code instead of trying to shoehorn in sync requests. It's much better to just adopt a coding style that revolves around async requests when working in javascript, especially where you're already doing AJAX (which is by definition intended to be async).
Pass async:false along with the ajax options..
$.ajax({
type: "POST",
async:false,
.
.
.
});
You can make your call only synchronous by using ajax prefilters:
function ShowData() {
//some code that determines the page number
$.ajaxPrefilter( function( options, originalOptions, jqXHR ) {
options.async = false;
});
GetRequest(ThePageNumber);
//wait until the data is in
};
All I need is a method that returns true if the Url is responding. Unfortunately, I'm new to jQuery and it's making my attempts at writing that method rather frustrating.
I've seen several examples of jQuery using .ajax, but the code is consistently failing on me. What's wrong?
var urlExists = function(url){
//When I call the function, code is still executing here.
$.ajax({
type: 'HEAD',
url: url,
success: function() {
return true;
},
error: function() {
return false;
}
});
//But not here...
}
That isn't how AJAX works. AJAX is fundamentally asynchronous (that's actually what the first 'A' stands for), which means rather than you call a function and it returns a value, instead you call a function and pass in a callback, and that callback will be called with the value.
(See http://en.wikipedia.org/wiki/Continuation_passing_style.)
What do you want to do after you know whether the URL is responding or not? If you intended to use this method like this:
//do stuff
var exists = urlExists(url);
//do more stuff based on the boolean value of exists
Then what you instead have to do is:
//do stuff
urlExists(url, function(exists){
//do more stuff based on the boolean value of exists
});
where urlExists() is:
function urlExists(url, callback){
$.ajax({
type: 'HEAD',
url: url,
success: function(){
callback(true);
},
error: function() {
callback(false);
}
});
}
urlExists() can not return because it needs wait for the request.
Either pass it a callback, or make it synchronous (not recommended, because it locks the browser).
var urlExists = function(url, callback) {
if ( ! $.isFunction(callback)) {
throw Error('Not a valid callback');
}
$.ajax({
type: 'HEAD',
url: url,
success: $.proxy(callback, this, true),
error: $.proxy(callback, this, false)
});
};
Then you can do
urlExists('/something', function(success) {
if (success) {
alert('Yay!');
} else {
alert('Oh no!');
}
});
It also worth mentioning the same origin policy.
Also, returning from an anonymous function's scope will not return in the parent function (like in your original example). It just returns that inner function. To return from an inner to a parent, set a flag and return it.
Basically, there is nothing wrong with your code. See it work here:
http://jsfiddle.net/PK76X/
My guess is that you're using it to check the availability of content on a different domain, which fails because browsers don't allow cross domain ajax-requests.
If the url is from the same domain as your page you can do it. But if it is from a different domain, for example google.com, then it will fail due to cross domain security.
In general, you should probably run your script in Firefox using the firebug plugin. It will give you the details needed to solve the issue.
The ajax and post methods are asynchronous, so you should handle the result in a callback method.
AJAX is basically asynchronous, and that's why the behavior you are describing.
I've used the following, which is free of cross origin, to get a simple true/false indication whether a URL is valid, in a synchronous manner:
function isValidURL(url) {
var encodedURL = encodeURIComponent(url);
var isValid = false;
$.ajax({
url: "http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20html%20where%20url%3D%22" + encodedURL + "%22&format=json",
type: "get",
async: false,
dataType: "json",
success: function(data) {
isValid = data.query.results != null;
},
error: function(){
isValid = false;
}
});
return isValid;
}
The usage is then trivial:
var isValid = isValidURL("http://www.wix.com");
alert(isValid ? "Valid URL!!!" : "Damn...");
Hope this helps