Checking if a URL exists or not in Client Side Code - javascript

My objective is to check whether a URL is valid or not from client side. I tried the following things:
1. Tried using a ajax request using dataType as JSON. - Got the Cross-Origin Request Blocked error.
2. Tried using the JSONP as datatype. - Worked fine for some websites like google.com but it cribed for others like facebook.com
Got the error like "Refused to execute script from
FaceBook
callback=jQuery32107833494968122849_1505110738710&_=1505110738711'
because its MIME type
('text/html') is not executable, and strict MIME type checking is enabled."
Is there any workaround for this. I just want to make sure that the URL is valid irrespective of the content in the response.
Following is the code I wrote:
<html>
<body>
<script
src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js">
</script>
<script>
function CallPageMethod() {
$.ajax({
type: "GET",
url: "https://www.google.com/",
dataType: "jsonp",
success: function (data, textStatus, xhr) {
alert("Success");
},
error: function (data, textStatus, xhr) {
if (data.status === 200) {
alert("Finally I am done")
} else {
alert("Error");
}
},
});
}
</script>
<Button onclick="CallPageMethod()">Test URL</Button>
</body>
</html>
Any Suggestions or any alternative approach that I should follow to resolve this issue?

Not properly, but Most sites have a favicon.ico either from the site directly or provided from the hosting company for the site if it is a 404 image.
<img src="https://www.google.com/favicon.ico"
onload="alert('icon loaded')">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"
onload="alert('ajax loaded')"></script>
Although iframe and object do have onload events, invalid pages also trigger the event.
This would be the fastest site test I can think of ...
var img = new Image();
img.onload = function () {
alert("image width is " + img.naturalWidth + " not zero so site is valid");
}
img.src = "https://www.google.com/favicon.ico";
As for facebook, the each page uses resources from another url, iframes are blocked as well as scripts. You would need to make the request from a server to test if a page existed.

You're best off writing a proxy on your server so:
Client hits your server with the URL you want to check
Your server makes the request to that URL and gets a response (or not)
Server returns status code to the client
This way will avoid the CORS issues you're having to navigate and will allow you to set any HTTP headers you need to.

Related

Ajax URL appears blocked by company firewall

I am working on an ajax function that loads another page as a way to get around iframe limitations on Shopify. My issue seems to be that the URL is blocked or headers stripped. Nothing too complex, everything worked as I needed it to by using the following:
function get_report() {
var params = {
type: "GET",
url: "https://example.com/mypage.php",
dataType: 'html',
success:function(html) {
$("#content_div").load("https://example.com/mypage.php");
},
error: function(XMLHttpRequest, textStatus) {
alert('Error : ' +XMLHttpRequest.response);
}
};
jQuery.ajax(params);
};
<button onclick="get_report()">Get</button>
<div id="content_div"></div>
This works through public networks with no problem. However, when my client uses it behind a company firewall it fails to load the page. Upon further inspection it appears that the site URL my php is hosted on cannot be loaded either (I cannot be there to physically confirm). Here is a sample of that page if its relevant:
<?php
$allowedOrigins = [
"https://myexample.com",
"https://myexample2.com"
];
if (array_key_exists('HTTP_ORIGIN', $_SERVER)) {
$origin = $_SERVER['HTTP_ORIGIN'];
} else if (array_key_exists('HTTP_REFERER', $_SERVER)) {
$origin = $_SERVER['HTTP_REFERER'];
} else {
$origin = $_SERVER['REMOTE_ADDR'];
}
if (in_array($origin, $allowedOrigins)) {
header("Access-Control-Allow-Origin: " .$origin);
}
setcookie('cross-site-cookie', 'name', ['samesite' => 'None', 'secure' => true]);
?>
<!DOCTYPE HTML>
<html lang="en">
<head>
<meta charset="utf-8">
<title>TEST ALT IFRAME</title>
</head>
<body>
<div><?php echo "IT WORKS"; ?></div>
</body>
</html>
What I know:
-Walked client through accessing chrome console, zero errors listed
-URL never loads when client tries to load it via browser
-Ajax never gives an error response
-Webmaster/IT team is unreachable (I have tried to contact them for at least 4 months)
What I've tried:
-Recently adding meta tags and !DOCTYPE (just in case)
-Validating both the iframe site and URL site with W3C
-Confirming both the iframe site and URL site work with VPN and public networks
-Checking for correct categorization on major network filtering groups (semantics, paleo-alto, etc) and set to 'SAFE'.
My Question:
-How do I find out if the URL is blocked or the ajax request is being stripped?
-If the network is filtering my ajax URL am I at a dead end or is there another option?
How do I find out if the URL is blocked or the ajax request is being stripped?
If there's a network error, you can respond to it in the error callback you pass to the AJAX call:
function get_report() {
var params = {
type: "GET",
url: "https://example.com/mypage.php",
dataType: 'html',
success:function(html) {
$("#content_div").load("https://example.com/mypage.php");
},
error: function(XMLHttpRequest, textStatus) {
// inspect XMLHttpRequest to determine if network error occurred
alert('Error : ' +XMLHttpRequest.response);
}
};
jQuery.ajax(params);
};
If the network is filtering my ajax URL am I at a dead end or is there another option?
You're sort of at a dead end at the application level, unless you're willing to do something really convoluted like have a third party service, that you know will not have firewall restrictions, request the page, and then forward it to a service that is accessible from behind that firewall. So the short answer is, no, not really (at least not practically)

JQuery ajax GET request to URL fails although HTTP status is 200 OK

I apologize if this question has already been answered.
I am trying to retrieve data from a REST web service that exposes a JSON interface using jQuery .ajax call.
When I call the service using the URL, the jQuery call fails although I get a HTTP status code 200 OK.
When I copy the response into a file on the filesystem and retrieve this, the same call works.
Both the file I am accessing and the web service I am calling are on the same machine.
Some notes on the url used in the code below:
Using:
url: "http://localhost:9090/app/user/861",
the call fails, goes into .fail on all browsers.
The URL itself returns the json on all browsers:
{
"userid": 861,
"employeeno": "123",
"jobdesc": "Developer",
"firstname": "Jasper",
"lastname": "Fitussi"
}
when using "test.json" in the local filesystem following is the behavior:
url: "ajax/test.json",
On Firefox, the call executes, goes into .done and displays the result on page.
On Chrome, the call fails with status 404 and the following message -
"No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access."
I tried different combinations changing dataType:"jsonp", adding a ?callback=? to the end of the URL, and enclosing the data in the test.json with a '(' and a ')' without luck.
Please understand I am new to UI programming, javascript and jQuery.
Please help with what I am doing wrong. Here's the javascript:
<script src="http://code.jquery.com/jquery-1.10.2.js" type="text/javascript">
</script>
<script type="text/javascript">
$(document).ready(function () {
$.ajax({
type: "GET",
url:"ajax/test.json",
// the following commented call fails, goes into .fail
// url:"http://localhost:9090/app/user/861",
contentType: "application/json",
accepts: "application/json",
dataType: "json"
})
.done(function(data) {
alert("Success");
console.log(data);
var items = [];
$.each( data, function( key, val ) {
items.push( "<li id='" + key + "'>" + val + "</li>");
});
$( "<ul/>", {
"class": "my-new-list",
html: items.join( "" )
}).appendTo( "body" );
})
.fail(function(data) {
console.log(data);
alert("Failed");
})
.always(function() {
alert("In Always");
});
});
</script>
The following is the output when I paste the url into the browser (also the contents of ajax/test.json):
{
"userid": 861,
"employeeno": "123",
"jobdesc": "Developer",
"firstname": "Jasper",
"lastname": "Fitussi"
}
Your problem is not about UI programming, it's about the security model of modern browsers :p
Access-Control-Allow-Origin errors occurs when you call a webservice (ie: load a JSON file) from a domain that is different from the one hosting your HTML page.
In your case, you are opening the html file from your hard drive (file:///) and calling a webservice on localhost.
This is a security feature in all modern browsers that forbid getting data from a foreign webservice without the webservice owners authorizing you (or everyone, wildcards are allowed) to call it.
I recommend reading the following guide from MDN, so that you understand WHY you are having this problem.
It will then be easy to resolve
https://developer.mozilla.org/en/docs/HTTP/Access_control_CORS
If you control the source code of the webservice, or the webserver hosting it, you need to add Access-Control-Allow-Origin HTTP headers.
Do you make your ajax call using Apache on wamp, lamp, xampp or mamp or not? I think you work directly using some files lets say on your desktop and not from the www file of wamp. If the browser sends a correct url then the backend responds great, your frontend code seems fine so i think chrome complains about your not using localhost. Am i right? Whats your local development setup?
If it's a local file on the client-side, use file:/// to prefix the URL:
url: 'file:///ajax/test.json'
The third / in file:/// indicates:
As a special case, can be the string "localhost" or the empty
string; this is interpreted as `the machine from which the URL is
being interpreted'.
3.10
Reference here
Download a tool called fiddler, from http://fiddler2.com/ great way to debug web requests and to see why they are failing.
This will help you narrow down the issue you are experiencing and we can help you further because currently its all guess work.
I had the same issue, all worked fine in I.E and FireFox, a had one ajax call to a rest service using jsonp and it worked fine in chrome, however when I tried to load a file using jsonp I got the cross domain error. In short i had to add "file:" to my file path in the url
$.ajax({
type : 'GET',
url : 'file:jsondata/rain_acc_data.json',
dataType : 'jsonp',
jsonpCallback : "jsoncallback",
success : function(data) {
aler('ok');
},
error : function(jqXHR, status) {
alert("Failed to load list" + status + jqXHR);
}
});
this worked for me, make sure to wrap your json in the file with jsoncallback("your jason here");

AJAX get: anonymous function not being called upon success

I know I must be missing something obvious, but I can't seem to see why my code/approach doesn't work. When I try to call an anonymous function upon success in my AJAX call (I'm just trying to grab an XML file), it never fires. If, however, I change the success to a mere alert('success!') This works fine. Can anyone shed light on why this is happening?
$("#target").click(function() {
alert( "Handler for .click() called." );
var part = document.getElementById('partname').value;
var url = "http://parts.igem.org/xml/part." + part;
alert(url);
$.ajax({
type: 'GET',
url: url,
dataType: 'xml',
success: function(response) {
console.log('response = '+response);
}
});
});
Again, using:
success: alert('success');
In lieu of the anonymous function works fine. Completely puzzled over here. Thank you!
AJAX calls have to come from the same domain or site because of the same origin policy...
The same origin policy prevents a document or script loaded from one
origin from getting or setting properties of a document from another
origin. This policy dates all the way back to Netscape Navigator 2.0.
one of the usual ways to get XML from another site is to use PHP and CURL. you have only listed client side languages, though. I would look into other methods of getting this data...
Why does this policy exist?
You could try implementing CORS, but that would require you to have access to the other domain. You would need to set a response header at the requested domain of "ACCESS-CONTROL-ALLOW-ORIGIN:*" or "ACCESS-CONTROL-ALLOW-ORIGIN:http://www.domainThatMakesTheRequest.com"

How to detect an error 404 in an iframe?

My Web page uses iframes to collect content from other pages. All pages are in the same domain.
From the main page, is there a way to confirm that all iframes have loaded, and that there is no 404 error?
The status only lives in the response header.
The 404 Page is handling an HTTP Status Code, which is only included in the server's response sent to the browser, but not in the actual window and document objects of the DOM that javascript may access. This means that while you certainly can collect the status-code and take appropriate actions, you may only do so when your javascript is receiving the response, such as with a jQuery.ajax() request or an XmlHttRequest to load your "iframe".
Hope the 404 page follows 404 standards.
If the above isn't an option, the only other possibility may be to check the title, and/or H tags, for " 404 ". While this is most certainly less than ideal (I'd love to see, "404, Movie not Found, the Movie."), it is your only other option.
$('#iframe').load(function (e) {
var iframe = $("#iframe")[0];
if ( iframe.innerHTML() ) {
// get and check the Title (and H tags if you want)
var ifTitle = iframe.contentDocument.title;
if ( ifTitle.indexOf("404")>=0 ) {
// we have a winner! probably a 404 page!
}
} else {
// didn't load
}
});
Suppose this is your html
<html>
<head></head>
<body>
<iframe id="iframe"></iframe>
</body>
</html>
There are two scenario
Your iframe's src is in the same domain from where your page is originated.
Ex : page url www.example.com and iframe's src www.example.com/iframe
You can use jQuery ajax request to check if the the resource is available
$(function() {
$.ajax({
type : "HEAD",
async : true,
url : "www.example.com/iframe"
})
.success(function() {
$("#iframe").attr("src", "www.example.com/iframe");
})
.error(function(){
// Handle error perhaps a failover url
})
});
Your iframe's src is not pointing to the same domain from where your page was originated.
Ex : Page url www.example.com and iframe's src www.otherdomain.com/iframe
Now browsers will not let you make a cross site request from javascript code due to cross origin policy. The way around is to make a jsonp request.
$(function() {
$.ajax({
url: "www.otherdomain.com/iframe",
dataType: "jsonp",
timeout: 5000,
success: function () {
$("#iframe").attr("src", "www.otherdomain.com/iframe");
},
error: function (parsedjson) {
if(parsedjson.status == "200") {
$("#iframe").attr("src", "www.otherdomain.com/iframe");
} else {
// Handle error
}
}
});
});

API call over jQuery

I'm trying to build a .js file that sends data to an external API, waits for a response and interprets the results. The external API is XML-based and accepts an HTTPS Post with the XML as body (content-type; text/xml). I can call the API correctly via cURL.
This is what I have so far:
<html>
<head>
<script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body onload="CallService()">
<script type="text/javascript">
var webServiceURL = 'https://www.url.com';
var xmlString = '<xml><parameter1>value1</parameter1>
<parameter2>value2</parameter2></xml>';
function CallService() {
$.ajax({
url: webServiceURL,
type: "POST",
dataType: "xml",
data: xmlString,
processData: false,
contentType: "text/xml; charset=\"utf-8\"",
success: OnSuccess,
error: OnError
});
return false;
}
function OnSuccess(data, status) {
alert(data.d);
}
function OnError(request, status, error) {
alert('error');
}
$(document).ready(function() {
jQuery.support.cors = true;
});
</script>
</body>
</html>
When I open the HTML I get an alert saying "error" and nothing appears on the other end (the external API's). Is there a way to do this using just JavaScript/Ajax/jQuery or do I need a "supporting" code that receives the JS call?
When you want to make cross domain queries, you have basically 3 types of solution :
1) use JSONP, which won't interest you if you're using XML and not JSON
2) not really do cross-domain, by setting a kind of proxy (or any type of get) on the server serving the main html page
3) changing headers on the server to specify to the browser that you accept cross-domain queries. This is new but yet accepted by all major browsers. That's called CORS. It's easy to change the headers ("Access-control-...") in all server-side languages so that should now be the preferred way (if you have issues (security, rights, bandwidth, ad, etc.) with cross-domain access to the data you serve, you can restrain the allowed origins).

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