AJAX request status returns 0 - javascript

when i make a AJAX request with this code, it returns the status as 0. what did i do wrong? Also, this code is only designed to work in Firefox for various reasons.
var ajax;
function connectToOtherServer(server,port,userid,password){
ajax=new XMLHttpRequest();
ajax.onreadystatechange=validateConnection;
params='userid='+encodeURIComponent(userid)+'&password='+encodeURIComponent(password);
alert('http://'+server+':'+port+'/ok.txt');
ajax.open('POST','http://'+server+':'+port+'/ok.txt',true);
ajax.setRequestHeader("Content-type","application/x-www-form-urlencoded");
ajax.setRequestHeader("Content-length",params.length);
ajax.setRequestHeader("Connection","close");
ajax.send(params);
}
function validateConnection(){
if(ajax.readyState===4){
if(ajax.status===200){
alert(ajax.responseText);
}else{
alert(ajax.status);
}
}
}

If you try to connect to another server, the same origin policy will stop you:
The term "origin" is defined using the
domain name, application layer
protocol, and (in most browsers) TCP
port of the HTML document running the
script. Two resources are considered
to be of the same origin if and only
if all these values are exactly the
same.

jquery.com You can only connect to another server if you use JSONP and a callback. The other server will need to support the JSONP/callback mechanism. This method involves creating a new script tag then having the remote server return the callback code into this script tag. Look at the jQuery source code (or simply use it) to see it handles JSONP.
The basic idea is to create a script tag with the source as the remote URL. The remote method returns a "script" containing a function call using the callback and the resultant JSON data.

I've recently run into this issue. I've been using AJAX to submit form results so that page elements can update automatically. My domain calls were correct. SELECT statements on the database would work, but INSERT, UPDATE, and DELETE statements would not.
Alerts showing progress through the javascript indicated that the call was running correctly, but it would never make it to the php portion of the process. The simple answer was that the form's onsubmit element needed to include return false;. After adding that, the things ran smoothly.
<form name="form" action="" method="post" onsubmit="ProcessRequest(this);return false;">
Hope this helps.

Related

How to send a request from JavaScript without base URL?

I'd like to send a request to a simple URL from my JavaScript, so that the base URL will NOT be added to the request URL. For example, the request should be sent to the following URL (without the base URL):
SAPEVENT:SOME_TEXT?2
I used the jQuery's $.ajax function in order to implement it, but without success.
Here is a JSFiddle for it:
http://jsfiddle.net/txb6tdjj/2/
The JS code:
function sendEvent(id) {
$.ajax("SAPEVENT:SOME_TEXT?" + id);
}
sendEvent(2);
I see the following error in the JS console:
XMLHttpRequest cannot load sapevent:SOME_TEXT?2. Cross origin requests
are only supported for HTTP. (jquery-2.1.0.js:8556)
I even set the parameter crossDomain: true, but it didn't help:
http://jsfiddle.net/auhx2v2v/3/
The JS code:
function sendEvent(id) {
$.ajax({
url: "SAPEVENT:SOME_TEXT?" + id,
crossDomain: true
});
}
sendEvent(2);
It ends up with the same error.
It works correct in the HTML like this:
http://jsfiddle.net/1f6npcn2/2/
The HTML code which works correctly:
<FORM action="SAPEVENT:PRESS_ME">
Click on me to send an event!
<INPUT TYPE="submit" VALUE="Press me to send an event!"/>
</FORM>
But I need to implement it in JavaScript, so that a request parameter can be set dynamically in the URL in JavaScript.
Do you know how to implement it in JS so that the request will be sent to the URL SAPEVENT:SOME_TEXT?2 without the base URL?
Additional information about used browsers: The error is shown only in Chrome. IE and Firefox do not show an error, but they also don't send the request.
Additional information for the SAP guys: I know there is a SAP Note 191908 which states that it's impossible, but a colleague has confirmed that he has successfully tested such functionality in an HTML page which used the same code as I copied above (see the HTML code above and http://jsfiddle.net/1f6npcn2/2/). So the SAP Note is wrong. I know how I can implement this functionality in HTML, but I don't know how I can implement it in JS. That's the problem.
I have no experience of working with SAP but I think you are missing a crucial part here.
In the samples you gave SAPEVENT:CLICK_ON_ME isn't a http url at all but rather it would invoke whatever handles the SAPEVENT-protocol on the local computer with the parameter CLICK_ON_ME. I'm guessing that you have some sort of client installed on your computer that does this for you (how do I create my own URL protocol? (e.g. so://...) contains some more information on how this is accomplished).
The reason your error-message talks about crossdomain-stuff is probably because it tried to interpret it as host:port.
So in other words, since this isn't a http url there isn't a webserver working on the other end so you can't do ajax-requests against it.
The SAPEVENT: stuff is not handled by any web server. The SAP GUI uses an embedded Internet Explorer and registers a custom protocol handler. There is no use in trying to use ajax techniques since you need to reach the container of the client, not the server. To reiterate: You do not want to "send a request" anywhere, you want to convince the browser that a certain local navigation event happened". SAP Note 191908 contains more information on that topic.
No idea about SAP Views, but to me this seems like a usual behaviour on webservers. I presume that SAPEVENT gets parsed by the server during the runtime to a more regular URI. Only the views get parsed, not the resources like CSS and JS, so the SAPEVENT placeholders in the JS file don't get parsed and the JS interpreter will not accept it as a valid URI. One of the common ways of solving this, is to create either a hidden form in the HTML or just a hidden input containing the server-generated values you are needing. For example
SAP View:
<input type="hidden" id="my_event_url" value="SAPEVENT:PRESS_ME">
JS:
function sendEvent(id) {
$.ajax({
url: $('#my_event_url').val() + '?' + id,
crossDomain: true
});
}
sendEvent(2);
I finally implemented it in JavaScript. Thanks go to this web page.
I modified the solution which was shown in this web page in order to add a link instead of a form in JavaScript.
This is the working solution in JS:
var targetUrl = "SAPEVENT:SOME_TEXT?2";
function sendSapEvent(targetUrl) {
var link = document.createElement("a");
link.setAttribute("style", "display:none;");
link.setAttribute("href", targetUrl);
// Move the click function to another variable
// so that it doesn't get overwritten.
link._click_function_ = link.click;
document.body.appendChild(link);
link._click_function_();
}
sendSapEvent(targetUrl);
You can find it also in this JSFiddle: http://jsfiddle.net/708r95p0/6/
It works! It sends a request to the URL sapevent:SOME_TEXT?2
I decided to use a link instead of a form element, bacause I couldn't pass the request parameter using a form.

Why JavaScript function fires before .NET action?

I noticed that when a link on the page has JS onclick function and also a MVC action method, the JS function fires before the action.
Wondering is this always the case?
Why/how browsers deside to run JS and the the backend method?
Can I run backend method first, but still want to fire the JS function?
Regards
Wondering is this always the case?
Why/how browsers deside to run JS and the the backend method?
Client-side JavaScript runs on the client, inside a page. Server-side .NET code runs on the server and generates an HTML document (or other resource).
To run server side code, the browser has to make an HTTP request.
The easiest way to make an HTTP request is to leave the current page and load a new one from the server (by following a link or submitting a form).
Since client-side JavaScript runs in a page, it can't run after the browser has left the page it runs in.
Can I run backend method first, but still want to fire the JS function?
You can make an HTTP request from JavaScript (before doing other JS actions) instead of leaving the current page. This is usually done with the XMLHttpRequest object and is known as Ajax.
Why/how browsers deside to run JS and the the backend method?
server side code will need a request to return the response. HTTP works on Request and Response architecture. basically client make requests in order to get the response (i.e results or desired data)
wheenever you do postback or return true to the server, it will execute server side methods.
ClickHereToSee
here return value which is returned by the function, if you return the true value it will go to the server method, if you returned the false it will prevent the default action.
Can I run backend method first, but still want to fire the JS function?
You can. use Ajax. basically Ajax requests are XMLHTTPRequest. which used to update the paritial portions.
Can I run backend method first, but still want to fire the JS function?
First two answers are already well answered. For third one you can try Jquery Ajax-
function SomeFunction(){
$.ajax({
type: 'POST',
url: "#Url.Content("Controller/ActionResult")",
data : {
*yourparameter:value* //data
},
dataType: 'json',
success:function(result)
{
//javascript stuff
}
});
}
ClickHereToSee

Asynchronous cross-domain POST request via JavaScript?

I could just create a form and use that to do a POST request to any site, thing is the FORM method isn't asynchronous, I need to know when the page has finished loading. I tried messing around with this using an iframe with a form inside, but no success.
Any ideas?
EDIT
unfortunately I have no control over the response data, it varies from XML, json to simple text.
You can capture the onload event of an iframe. Target your form to the iframe and listen for the onload. You will not be able to access the contents of the iframe though, just the event.
Try something like this:
<iframe id='RS' name='RS' src='about:blank' onload='loaded()'></iframe>
<form action='wherever.php' target='RS' method='POST'>...</form>
script block:
var loadComplete = 0
function loaded() {
//avoid first onload
if(loadComplete==0) {
loadComplete=1
return()
}
alert("form has loaded")
}
IF you want to make cross domain requests you should either made a JSON call or use a serverside proxy. A serverside proxy is easy to set up, not sure why people avoid it so much. Set up rules in it so people can not use the proxy to request other things.
If the data returned from the cross domain post is JSON, then you can dynamically add a script tag pointing to the URI that returns the data. The browser will load that "script" which then you can access from other javascript.
YUI3's IO object offers cross-domain requests, however it does so using a small Flash control it embeds on the page.
While there is work going into secure cross-domain requests from JavaScript, at this time, you need to use a plugin like Flash or Silverlight as a bridge with which to make the request.
You can't do anything cross-domain using javascript. You'd have to use a backend language like PHP or asp or something.

detecting JSON loaded by browser

I have an application in which most requests are submitted via AJAX, though some are submitted via "regular" HTTP requests. If a request is submitted and the user's session has timed out, the following JSON is returned:
{"authentication":"required"}
The JavaScript function which submits all AJAX requests handles this response by showing a popup message and redirecting the user back to the login page.
However, when a non-AJAX request receives this response the JSON is simply shown in the browser because the response is processed directly by the browser (i.e. the aforementioned JavaScript function is bypassed). Obviously this is not ideal and I would like the non-AJAX requests that receive this response to behave the same as the AJAX requests. In order to achieve this, I can think of 2 options:
Go through the application and convert all the requests to AJAX requests. This would work, but could also take a long time!
The JSON shown above is generated by a very simple JSP. I'm wondering if it might be possible to add a JavaScript event handler to this JSP which is run just before the content is displayed in the browser - I'm assuming this would never be called for AJAX requests? This handler could call the other JavaScript code that displays the popup and performs the redirection.
If anyone knows how exactly I can implement the handler I've outlined in (2), or has any other potential solutions, I'd be very grateful if they'd pass them on.
Cheers,
Don
3) Change your AJAX code to add a variable to the GET or POST: outputJson=1
You cannot add a handler to the JSP that way. Anything you add to it will make it a non-JSON producing page.
There are two options that I can see:
Add a parameter to the page by appending a URL parameter to the screen that modifies the output.
URL: http://domain/page.jsp?ajaxRequest=true
would output json only
URL: http://domain/page.jsp
would display a jsp page that could forward to another page.
OR
change the response to have the forwarding code in the JSP that will get executed by the web browser if it is hit directly. Then have your calling AJAX to strip the forwarding code out, and then process what is left.
4) Read up on the 'Accept' request HTTP header.
Then, on the server side tailor the output:
e.g.
if(Accept contains application/json...) { // client asking for json, likely to be XHR
return {"foo":"bar"}
} else { // other
return "Location: /login-please";
}
Start with a smarter error message, like this:
{"error":"authentication required"}
Wrap the JSON output in a callback:
errorHandler({"error":"authentication required"});
Have a handler waiting in your script:
function errorHandler(r) {
alert(r.error);
}
And don't forget to send it down as text/javascript and not application/x-json.

Access to restricted URI denied code: 1012

How do you get around this Ajax cross site scripting problem on FireFox 3?
If you're using jQuery it has a callback function to overcome this:
http://docs.jquery.com/Ajax/jQuery.ajax#options
As of jQuery 1.2, you can load JSON
data located on another domain if you
specify a JSONP callback, which can be
done like so: "myurl?callback=?".
jQuery automatically replaces the ?
with the correct method name to call,
calling your specified callback. Or,
if you set the dataType to "jsonp" a
callback will be automatically added
to your Ajax request.
Alternatively you could make your ajax request to a server-side script which does the cross-domain call for you, then passes the data back to your script
To update the answer (I guess, mostly for my benefit when I come looking for this answer later on), if are loading XML or something else, you can always ask the user if he will allow us to read from another site with this code:
try {
if (netscape.security.PrivilegeManager.enablePrivilege)
netscape.security.PrivilegeManager.enablePrivilege("UniversalBrowserRead");
} catch (e) {
alert("Sorry, browser security settings won't let this program run.");
return;
}
(from the RESTful web services book) But, this only works in firefox, when the html file is loaded from local file. So, not that useful.
One more solution: if all you need is the headers, you can specify "HEAD" as the method and it won't trigger the security issue. For instance, if you just want to know if the web page exists.
var client = new XMLHttpRequest();
client.open("HEAD", my_url, false);
client.send(null);
if(client.readyState != 4 || client.status != 200) //if we failed
alert("can't open web page");
Some more details would be nice: which AJAX library are you using, what would you like to achive, how you do it.
For example it can be a cross-domain Ajax request, which is not allowed. In this case use JSON.
I came across this problem recently and it was while I as AJAX loading the local request, not cross site scripting problem. Also, Jimmy himself seems to have the same problem. This seems to be the FF security problem, this article describes the cause and the solution to access to restricted uri denied" code: "1012 problem.
Sorry, got that error using JQuery
$.ajax on FireFox 3. Tried jsonp
suggestion but I think that will only
work with something that will serve up
json. I'm trying to create a sample
local html file based mashup that will
pull data from Yahoo!Finance, but they
are serving .csv, so I think I'm SOL.
– Jimmy Chandra (Sep 9 at 17:20)
I hope you'll find it useful.

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