I'm making a web app that requires that I check to see if remote servers are online or not. When I run it from the command line, my page load goes up to a full 60s (for 8 entries, it will scale linearly with more).
I decided to go the route of pinging on the user's end. This way, I can load the page and just have them wait for the "server is online" data while browsing my content.
If anyone has the answer to the above question, or if they know a solution to keep my page loads fast, I'd definitely appreciate it.
I have found someone that accomplishes this with a very clever usage of the native Image object.
From their source, this is the main function (it has dependences on other parts of the source but you get the idea).
function Pinger_ping(ip, callback) {
if(!this.inUse) {
this.inUse = true;
this.callback = callback
this.ip = ip;
var _that = this;
this.img = new Image();
this.img.onload = function() {_that.good();};
this.img.onerror = function() {_that.good();};
this.start = new Date().getTime();
this.img.src = "http://" + ip;
this.timer = setTimeout(function() { _that.bad();}, 1500);
}
}
This works on all types of servers that I've tested (web servers, ftp servers, and game servers). It also works with ports. If anyone encounters a use case that fails, please post in the comments and I will update my answer.
Update: Previous link has been removed. If anyone finds or implements the above, please comment and I'll add it into the answer.
Update 2: #trante was nice enough to provide a jsFiddle.
http://jsfiddle.net/GSSCD/203/
Update 3: #Jonathon created a GitHub repo with the implementation.
https://github.com/jdfreder/pingjs
Update 4: It looks as if this implementation is no longer reliable. People are also reporting that Chrome no longer supports it all, throwing a net::ERR_NAME_NOT_RESOLVED error. If someone can verify an alternate solution I will put that as the accepted answer.
Ping is ICMP, but if there is any open TCP port on the remote server it could be achieved like this:
function ping(host, port, pong) {
var started = new Date().getTime();
var http = new XMLHttpRequest();
http.open("GET", "http://" + host + ":" + port, /*async*/true);
http.onreadystatechange = function() {
if (http.readyState == 4) {
var ended = new Date().getTime();
var milliseconds = ended - started;
if (pong != null) {
pong(milliseconds);
}
}
};
try {
http.send(null);
} catch(exception) {
// this is expected
}
}
you can try this:
put ping.html on the server with or without any content, on the javascript do same as below:
<script>
function ping(){
$.ajax({
url: 'ping.html',
success: function(result){
alert('reply');
},
error: function(result){
alert('timeout/error');
}
});
}
</script>
You can't directly "ping" in javascript.
There may be a few other ways:
Ajax
Using a java applet with isReachable
Writing a serverside script which pings and using AJAX to communicate to your serversidescript
You might also be able to ping in flash (actionscript)
You can't do regular ping in browser Javascript, but you can find out if remote server is alive by for example loading an image from the remote server. If loading fails -> server down.
You can even calculate the loading time by using onload-event. Here's an example how to use onload event.
Pitching in with a websocket solution...
function ping(ip, isUp, isDown) {
var ws = new WebSocket("ws://" + ip);
ws.onerror = function(e){
isUp();
ws = null;
};
setTimeout(function() {
if(ws != null) {
ws.close();
ws = null;
isDown();
}
},2000);
}
Update: this solution does not work anymore on major browsers, since the onerror callback is executed even if the host is a non-existent IP address.
To keep your requests fast, cache the server side results of the ping and update the ping file or database every couple of minutes(or however accurate you want it to be). You can use cron to run a shell command with your 8 pings and write the output into a file, the webserver will include this file into your view.
The problem with standard pings is they're ICMP, which a lot of places don't let through for security and traffic reasons. That might explain the failure.
Ruby prior to 1.9 had a TCP-based ping.rb, which will run with Ruby 1.9+. All you have to do is copy it from the 1.8.7 installation to somewhere else. I just confirmed that it would run by pinging my home router.
There are many crazy answers here and especially about CORS -
You could do an http HEAD request (like GET but without payload).
See https://ochronus.com/http-head-request-good-uses/
It does NOT need a preflight check, the confusion is because of an old version of the specification, see
Why does a cross-origin HEAD request need a preflight check?
So you could use the answer above which is using the jQuery library (didn't say it) but with
type: 'HEAD'
--->
<script>
function ping(){
$.ajax({
url: 'ping.html',
type: 'HEAD',
success: function(result){
alert('reply');
},
error: function(result){
alert('timeout/error');
}
});
}
</script>
Off course you can also use vanilla js or dojo or whatever ...
If what you are trying to see is whether the server "exists", you can use the following:
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;
}
This will return a true/false indication whether the server exists.
If you want response time, a slight modification will do:
function ping(url) {
var encodedURL = encodeURIComponent(url);
var startDate = new Date();
var endDate = null;
$.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) {
if (data.query.results != null) {
endDate = new Date();
} else {
endDate = null;
}
},
error: function(){
endDate = null;
}
});
if (endDate == null) {
throw "Not responsive...";
}
return endDate.getTime() - startDate.getTime();
}
The usage is then trivial:
var isValid = isValidURL("http://example.com");
alert(isValid ? "Valid URL!!!" : "Damn...");
Or:
var responseInMillis = ping("example.com");
alert(responseInMillis);
const ping = (url, timeout = 6000) => {
return new Promise((resolve, reject) => {
const urlRule = new RegExp('(https?|ftp|file)://[-A-Za-z0-9+&##/%?=~_|!:,.;]+[-A-Za-z0-9+&##/%=~_|]');
if (!urlRule.test(url)) reject('invalid url');
try {
fetch(url)
.then(() => resolve(true))
.catch(() => resolve(false));
setTimeout(() => {
resolve(false);
}, timeout);
} catch (e) {
reject(e);
}
});
};
use like this:
ping('https://stackoverflow.com/')
.then(res=>console.log(res))
.catch(e=>console.log(e))
I don't know what version of Ruby you're running, but have you tried implementing ping for ruby instead of javascript? http://raa.ruby-lang.org/project/net-ping/
let webSite = 'https://google.com/'
https.get(webSite, function (res) {
// If you get here, you have a response.
// If you want, you can check the status code here to verify that it's `200` or some other `2xx`.
console.log(webSite + ' ' + res.statusCode)
}).on('error', function(e) {
// Here, an error occurred. Check `e` for the error.
console.log(e.code)
});;
if you run this with node it would console log 200 as long as google is not down.
You can run the DOS ping.exe command from javaScript using the folowing:
function ping(ip)
{
var input = "";
var WshShell = new ActiveXObject("WScript.Shell");
var oExec = WshShell.Exec("c:/windows/system32/ping.exe " + ip);
while (!oExec.StdOut.AtEndOfStream)
{
input += oExec.StdOut.ReadLine() + "<br />";
}
return input;
}
Is this what was asked for, or am i missing something?
just replace
file_get_contents
with
$ip = $_SERVER['xxx.xxx.xxx.xxx'];
exec("ping -n 4 $ip 2>&1", $output, $retval);
if ($retval != 0) {
echo "no!";
}
else{
echo "yes!";
}
It might be a lot easier than all that. If you want your page to load then check on the availability or content of some foreign page to trigger other web page activity, you could do it using only javascript and php like this.
yourpage.php
<?php
if (isset($_GET['urlget'])){
if ($_GET['urlget']!=''){
$foreignpage= file_get_contents('http://www.foreignpage.html');
// you could also use curl for more fancy internet queries or if http wrappers aren't active in your php.ini
// parse $foreignpage for data that indicates your page should proceed
echo $foreignpage; // or a portion of it as you parsed
exit(); // this is very important otherwise you'll get the contents of your own page returned back to you on each call
}
}
?>
<html>
mypage html content
...
<script>
var stopmelater= setInterval("getforeignurl('?urlget=doesntmatter')", 2000);
function getforeignurl(url){
var handle= browserspec();
handle.open('GET', url, false);
handle.send();
var returnedPageContents= handle.responseText;
// parse page contents for what your looking and trigger javascript events accordingly.
// use handle.open('GET', url, true) to allow javascript to continue executing. must provide a callback function to accept the page contents with handle.onreadystatechange()
}
function browserspec(){
if (window.XMLHttpRequest){
return new XMLHttpRequest();
}else{
return new ActiveXObject("Microsoft.XMLHTTP");
}
}
</script>
That should do it.
The triggered javascript should include clearInterval(stopmelater)
Let me know if that works for you
Jerry
You could try using PHP in your web page...something like this:
<html><body>
<form method="post" name="pingform" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<h1>Host to ping:</h1>
<input type="text" name="tgt_host" value='<?php echo $_POST['tgt_host']; ?>'><br>
<input type="submit" name="submit" value="Submit" >
</form></body>
</html>
<?php
$tgt_host = $_POST['tgt_host'];
$output = shell_exec('ping -c 10 '. $tgt_host.');
echo "<html><body style=\"background-color:#0080c0\">
<script type=\"text/javascript\" language=\"javascript\">alert(\"Ping Results: " . $output . ".\");</script>
</body></html>";
?>
This is not tested so it may have typos etc...but I am confident it would work. Could be improved too...
Related
I have integrated authorize.net accept.js embedded iFrame in my application. Having trouble setting the transaction respone in my lambda function to get the response. I've seen similar questions on stack overflow but nothing worked out for me yet.
Using Nodejs for my backend and angular7 for the front-end.
I successfully get the token from my lambda function so my iframe appears on the ui. I've set \"showReceipt\": false providing url for cancel & continue, since the documentation says I have to set the show receipt parameter "false" in order to communicate with the IFrameCommunicator.html in the ui. But when I click on "Pay" its stuck at "Processing.." for a long time.
Following are the request & response headers respectively from the network tab:
* Cookie: __cfruid=deb63d2f12d9690aeea838cf7f31ada6da92bc1c-1602260930
* Host: test.authorize.net
* Origin: https://test.authorize.net
* Referer: https://test.authorize.net/payment/payment
* Sec-Fetch-Dest: empty
* Sec-Fetch-Mode: cors
*
Sec-Fetch-Site: same-origin
{"resultCode":"Ok","messageCode":"Ok","transactionData":{"accountType":"Discover","accountNumber":"XXXX0012","transId":"40055282319","responseCode":"4","authorization":"TYIUU7","merchantName":"iMart Inc.","totalAmount":"1999.9","dateTime":"10/09/2020 4:20:27 PM"}}
I'm sure the transaction is happening looking at the response but not sure why it's not connecting with the communicator.
I've read the steps in the documentation and also followed the GitHub sample code-https://github.com/AuthorizeNet/accept-sample-app, which made me more confused since they both say different things at some places. Following are the steps I've accomplished until now :
Created a lambda hosted payment function with all the settings (followed the correct sequence) to get back a token.
Created a hosted payment form to display the iframe.
Able to make a payment --> get the receipt page --> routing to success screen.
What I'm trying to accomplish:
After I make the payment, initial idea was to trigger a different lambda function based on the response from authorize.net without communicating with IFrameCommunicator.html, but as I cannot do that, I want to get a response to initiate the next process at the backend.
Also, we're not storing any user details in our server and not interested in creating a customer profile unless it's a necessary step to get the transaction response. Please suggest the step integration if I can do it in the same lambda function I've created to get a token or I would have to create a different one for this and when will that step be implemented?
I know about the Webhooks but not sure if it's an absolute necessity at this point of time when I'm just trying to implement a simple transaction.
I'm a newbie and I couldn't find a lot of examples related to the same to resolve my issues/confusions. Would highly appreciate if I get a clear explanation on the steps here and where am I going wrong.
Following is the code -
accept-hosted.js Lambda function:
merchantAuthenticationType.setName('*****');
merchantAuthenticationType.setTransactionKey('******');
var transactionRequestType = new ApiContracts.TransactionRequestType();
transactionRequestType.setTransactionType(ApiContracts.TransactionTypeEnum.AUTHCAPTURETRANSACTION);
transactionRequestType.setAmount(Total);
var setting1 = new ApiContracts.SettingType();
var setting2 = new ApiContracts.SettingType();
var setting4 = new ApiContracts.SettingType();
var setting5 = new ApiContracts.SettingType();
var setting6 = new ApiContracts.SettingType();
var setting7 = new ApiContracts.SettingType();
var setting8 = new ApiContracts.SettingType();
var setting9 = new ApiContracts.SettingType();
var setting10 = new ApiContracts.SettingType();
var setting11 = new ApiContracts.SettingType();
setting2.setSettingName("hostedPaymentButtonOptions");
setting2.setSettingValue("{\"text\": \"Pay\"}");
setting1.setSettingName("hostedPaymentReturnOptions");
setting1.setSettingValue(
"{\"showReceipt\": false, \"url\": \"https://iMart.com/success.html\", \"urlText\": \"Continue\", \"cancelUrl\": \"https://iMart.com/error.html\", \"cancelUrlText\": \"Cancel\"}");
setting10.setSettingName("hostedPaymentOrderOptions");
setting10.setSettingValue("{\"show\": false, \"merchantName\": \"iMart Inc.\"}");
setting5.setSettingName("hostedPaymentPaymentOptions");
setting5.setSettingValue("{\"cardCodeRequired\": true, \"showCreditCard\": true, \"showBankAccount\": false}");
setting7.setSettingName("hostedPaymentShippingAddressOptions");
setting7.setSettingValue("{\"show\": false, \"required\": false}");
setting8.setSettingName("hostedPaymentBillingAddressOptions");
setting8.setSettingValue("{\"show\": false, \"required\": false}");
setting6.setSettingName("hostedPaymentSecurityOptions");
setting6.setSettingValue("{\"captcha\": true}");
setting4.setSettingName("hostedPaymentStyleOptions");
setting4.setSettingValue("{\"bgColor\": \"blue\"}");
setting9.setSettingName("hostedPaymentCustomerOptions");
setting9.setSettingValue("{\"showEmail\": false, \"requiredEmail\": false, \"addPaymentProfile\": true }");
setting11.setSettingName("hostedPaymentIFrameCommunicatorUrl");
setting11.setSettingValue("{\"url\": \"https://iMart.com/IFrameCommunicator.html\"}");
var settingList = [];
settingList.push(setting2);
settingList.push(setting10);
settingList.push(setting5);
settingList.push(setting7);
settingList.push(setting8);
settingList.push(setting6);
settingList.push(setting4);
settingList.push(setting9);
settingList.push(setting11);
settingList.push(setting1);
var alist = new ApiContracts.ArrayOfSetting();
alist.setSetting(settingList);
var firstname = new ApiContracts.UserField();
firstname.setName('First Name');
firstname.setValue(firstName);
var lastname = new ApiContracts.UserField();
lastname.setName('Last Name');
lastname.setValue(lastName);
var userFieldList = [];
userFieldList.push(firstname);
userFieldList.push(lastname);
var userFields = new ApiContracts.TransactionRequestType.UserFields();
userFields.setUserField(userFieldList);
var transactionSetting1 = new ApiContracts.SettingType();
transactionSetting1.setSettingName('duplicateWindow');
transactionSetting1.setSettingValue('120');
var transactionSetting2 = new ApiContracts.SettingType();
transactionSetting2.setSettingName('recurringBilling');
transactionSetting2.setSettingValue('false');
var transactionSetting3 = new ApiContracts.SettingType();
transactionSetting3.setSettingName('emailCustomer');
transactionSetting3.setSettingValue('true');
var transactionSetting4 = new ApiContracts.SettingType();
transactionSetting4.setSettingName('headerEmailReceipt');
transactionSetting3.setSettingValue('You are all set!');
var transactionSetting5 = new ApiContracts.SettingType();
transactionSetting5.setSettingName('footerEmailReceipt');
transactionSetting5.setSettingValue('This is the footer');
var getRequest = new ApiContracts.GetHostedPaymentPageRequest();
getRequest.setMerchantAuthentication(merchantAuthenticationType);
getRequest.setTransactionRequest(transactionRequestType);
getRequest.setHostedPaymentSettings(alist);
var ctrl = new ApiControllers.GetHostedPaymentPageController(getRequest.getJSON());
const basicAuth = encode.encode("*****", 'base64');
await axios({
method: 'post',
url: 'https://apitest.authorize.net/xml/v1/request.api',
headers: {
'Authorization': 'Basic '+basicAuth,
'Content-Type': 'application/json'
},
data:JSON.stringify(ctrl._request)
}).then(async (data : any)=>{
if(data.data.token) {
callback(null, data.data) ;
} else callErr(data);
});
async function callErr(data: any){
callback(null, res) ;
}
}
IFrameCommunicator.html:
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Iframe Communicator</title>
<script type="text/javascript">
//<![CDATA[
function callParentFunction(str) {
if (str && str.length > 0
&& window.parent
&& window.parent.parent
&& window.parent.parent.AuthorizeNetPopup
&& window.parent.parent.AuthorizeNetPopup.onReceiveCommunication)
{
// Errors indicate a mismatch in domain between the page containing the iframe and this page.
window.parent.parent.AuthorizeNetPopup.onReceiveCommunication(str);
}
}
function receiveMessage(event) {
if (event && event.data) {
callParentFunction(event.data);
}
}
if (window.addEventListener) {
console.log('addEventListener');
console.log(receiveMessage);
window.addEventListener("message", receiveMessage, false);
} else if (window.attachEvent) {
window.attachEvent("onmessage", receiveMessage);
}
if (window.location.hash && window.location.hash.length > 1) { callParentFunction(window.location.hash.substring(1));
}
//]]/>
</script>
</head>
<body>
</body>
</html>
Angular code for showing the iFrame:
<iframe id="add_payment" class="embed-responsive-item panel" name="add_payment" width="100%" frameborder="0" scrolling="yes">
</iframe>
</div>
<form id="send_token" action="" method="post" target="add_payment" >
<input id="token" type="hidden" name="token" />
</form>
I have been struggling a lot since many days now with a time crunch. Would be really helpful if someone provides me with a good insight here. Please let me know if additional info is required. Thank you in advance!!!
Here are the answer for all your question, I hope it works :
1)if you are using iFrame then iFrameCommunicator is mandatory
2)the success url can only be used when you set "showReceipt" as true, here you cannot navigate automatically to yoour success page, this is the link for "Continue" button which appears when "showReceipt" is allowed
3)If you want to trigger any function or want to navigate after the response then add the following code in your html file
<script type="text/javascript">
$(document).ready(function () {
window.CommunicationHandler = {};
function parseQueryString(str) {
var vars = [];
var arr = str.split('&');
var pair;
for (var i = 0; i < arr.length; i++) {
pair = arr[i].split('=');
vars[pair[0]] = unescape(pair[1]);
}
return vars;
}
window.CommunicationHandler.onReceiveCommunication = function (argument) {
console.log('communication handler enter', argument);
var params = parseQueryString(argument.qstr)
switch (params['action']) {
case "resizeWindow":
console.log('resize'); break;
case "successfulSave":
console.log('save'); break;
case "cancel":
console.log('cancel'); break;
case "transactResponse":
sessionStorage.removeItem("HPTokenTime");
console.log('transaction complete');
var transResponse = JSON.parse(params['response']);
console.log('transaction complete1', transResponse);
// window.location.href = '/checkout/complete';
}
}
//send the token
$('#send_hptoken').submit();
});
</script>
UPDATE: I failed to mention that I already read the suggested duplicate answer and it didn't get me any further as I didn't see how it related to my problem. The user ponury-kostek below, did however manage to explain it simply enough without all that clutter, for me to understand. So that's how I don't see it as a duplicate.
I'm trying to implement saving user data into a database when the user logs in with LinkedIn (to keep track of who watched my page). I found a tutorial that used jQuery, and I found a GitHub (here) page for conversion of jQuery to Vanilla JS, but I'm struggling to understand what I need to do to convert this specific statement.
I got the whole thing working using just that one line of jQuery, no problems - but I don't want to force users to load the jQuery lib!
I'll post the jQuery I'm trying to convert, the Vanilla JS solution I have so far, and the conversion "formula" suggested on the GitHub page:
jQuery I'm trying to convert:
$.post('saveUserData.php',
{
oauth_provider: 'linkedin',
userData: JSON.stringify(userData)
},
function(data){ return true; });
My attempt at a Vanilla JS solution
var theUrl = 'saveUserData.php';
var httpRequest = new XMLHttpRequest();
httpRequest.onreadystatechange = function (data) {
};
httpRequest.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
httpRequest.open('POST', theUrl);
httpRequest.send({oauth_provider:'linkedin',userData: JSON.stringify(userData)}, function(data){ return true; });
Error thrown:
script.js:10 Uncaught DOMException: Failed to execute 'setRequestHeader' on 'XMLHttpRequest': The object's state must be OPENED.
at saveUserData (http://localhost:8012/linkedCV/script.js:10:14)
at displayProfileData (http://localhost:8012/linkedCV/index.php:43:4)
at B.<anonymous> (https://platform.linkedin.com/js/framework?v=1.0.350-1429&lang=undefined:3350:17)
at B.runHandler (https://platform.linkedin.com/js/framework?v=1.0.350-1429&lang=undefined:172:9)
at B.<anonymous> (https://platform.linkedin.com/js/framework?v=1.0.350-1429&lang=undefined:3355:6)
at B.handleSuccessResults (https://platform.linkedin.com/js/framework?v=1.0.350-1429&lang=undefined:172:9)
at Object.g [as success] (https://platform.linkedin.com/js/framework?v=1.0.350-1429&lang=undefined:3243:4)
at Object.incoming (https://platform.linkedin.com/js/framework?v=1.0.350-1429&lang=undefined:817:38)
at _window_onMessage (https://platform.linkedin.com/js/framework?v=1.0.350-1429&lang=undefined:581:102)
My JS (in the index header):
<script type="text/javascript" src="//platform.linkedin.com/in.js">
api_key: thecorrectAPIkey aka 'Client ID'
authorize: true
onLoad: onLinkedInLoad
scope: r_basicprofile r_emailaddress
</script>
<script type="text/javascript">
// Setup an event listener to make an API call once auth is complete
function onLinkedInLoad() {
IN.Event.on(IN, "auth", getProfileData);
}
// Use the API call wrapper to request the member's profile data
function getProfileData() {
IN.API.Profile("me").fields("id", "first-name", "last-name", "headline", "location", "picture-url", "public-profile-url", "email-address").result(displayProfileData).error(onError);
}
// Handle the successful return from the API call
function displayProfileData(data){
var user = data.values[0];
document.getElementById("picture").innerHTML = '<img src="'+user.pictureUrl+'" />';
document.getElementById("name").innerHTML = user.firstName+' '+user.lastName;
document.getElementById("intro").innerHTML = user.headline;
document.getElementById("email").innerHTML = user.emailAddress;
document.getElementById("location").innerHTML = user.location.name;
document.getElementById("link").innerHTML = 'Visit profile';
document.getElementById('profileData').style.display = 'block';
saveUserData(user);
}
// Handle an error response from the API call
function onError(error) {
console.log(error);
}
// Destroy the session of linkedin
function logout(){
IN.User.logout(removeProfileData);
}
// Remove profile data from page
function removeProfileData(){
document.getElementById('profileData').remove();
}
</script>
GitHub conversion suggestion:
// jQuery
$.post('//example.com', { username: username }, function (data) {
// code
})
// Vanilla
var httpRequest = new XMLHttpRequest()
httpRequest.onreadystatechange = function (data) {
// code
}
httpRequest.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded')
httpRequest.open('POST', url)
httpRequest.send('username=' + encodeURIComponent(username))
Since this works perfectly as long as I use the suggested jQuery (the one I want to convert to Vanilla JS), it all works fine. So I'm going to assume the rest of the code of my page is not needed (the PHP for the DB connection and for saving user data to the DB).
https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/setRequestHeader
When using setRequestHeader(), you must call it after calling open(),
but before calling send().
var theUrl = 'saveUserData.php';
var httpRequest = new XMLHttpRequest();
httpRequest.onreadystatechange = function (data) {
};
httpRequest.open('POST', theUrl);
httpRequest.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
httpRequest.send({oauth_provider:'linkedin',userData: JSON.stringify(userData)}, function(data){ return true; });
I'm using some jQuery to display tweets but once the Twitter API limit is reached, the request is sent but just keeps loading and loading. This doesn't look good. I want to be able to determine if the request is taking too long and then obviously do stuff, like cancel the request, change the styling, etc.
So this is the code that sends the request:
var fileref = document.createElement('script');
fileref.setAttribute("type","text/javascript");
fileref.setAttribute("src", "http://search.twitter.com/search.json?q="+buildString+"&callback=TweetTick&rpp=50");
document.getElementsByTagName("head")[0].appendChild(fileref);
And this is the TweetTick function:
function TweetTick(ob)
{
var container=$('#tweet-container');
container.html('');
$(ob.results).each(function(el){
/* in here, a div is built for each tweet and then appended to container */
});
container.jScrollPane(); /* just adds the scrollbar */
}
You need to cache twitter api response on your server side.
How do I keep from running into the rate limit?
I had a very similar problem lately. I use this script by Remy Sharp for most of my twitter requests: http://remysharp.com/2007/05/18/add-twitter-to-your-blog-step-by-step/
What you need to realise is that the api timeout is per IP address. So if the api has timed out for you based on your testing, it won't have timed out for someone else on a different IP address. Now, if someone accessing the site is doing so within a corporation or business, and others in the same place are doing the same, that timeout will occur almost instantaneously.
To get around this you need to cache your results. The way I did this was as follows.
I created a twitter caching system using the following code:
$twitter_username = "tadywankenobi"; //
$number_of_tweets = "10";
$options[CURLOPT_URL] = 'http://api.twitter.com/1/statuses/user_timeline.xml?screen_name='.$twitter_username.'&count='.$number_of_tweets.'&include_rts=1';
$options[CURLOPT_PORT] = 80;
$options[CURLOPT_FOLLOWLOCATION] = true;
$options[CURLOPT_RETURNTRANSFER] = true;
$options[CURLOPT_TIMEOUT] = 60;
$tweets = cache($options);
$twxml = new SimpleXMLElement($tweets);
echo "<ul>";
for($i=0;$i<=($number_of_tweets-1);$i++){
$text = $twxml->status[$i]->text;
echo "<li>".auto_link_twitter($text)."</li>";
}
echo "</ul>";
function cache($options) {
$cache_filename = "/var/cache/tweets.xml";
if(!file_exists($cache_filename)){
$handle = fopen($cache_filename, 'w') or die('Cannot open file: '.$my_file);
fclose($handle);
}// Check if cache file exists and if not, create it
$time_expire = filectime($cache_filename) + 60*60; // Expire Time (1 hour) // Comment for first run
// Set time to check file against
if(filectime($cache_filename) >= $time_expire || filesize($cache_filename) == 0) {
// File is too old or empty, refresh cache
$curl = curl_init();
curl_setopt_array($curl, $options);
$response = curl_exec($curl);
curl_close($curl);
if($response){
file_put_contents($cache_filename, $response);
}
else{
unlink($cache_filename);
}
}else{
$response = file_get_contents($cache_filename);
}
return $response;
}
What the cache function at the end does is create a file on the server and stores the twitter xml feedback in there. The system then checks to see the age of that file and if it's younger than an hour old, it takes its results from there. Otherwise, it re-accesses twitter. You need to have the file writable in the /var/cache folder (create it if it's not there).
I've kinda hacked this code together a bit, so let me know if you run into any issues with it. It also uses an auto_link_twitter() function, which creates the links required within the twitter text. I didn't write that, so I'll try and find you a link to it now.
Hope that all helps,
T
UPDATE: I can't remember where I got the auto_link_twitter() function, so here it is. If the person who wrote it reads this post, my apologies, I couldn't find the source again.
function auto_link_twitter($text) {
// properly formatted URLs
$urls = "/(((http[s]?:\/\/)|(www\.))?(([a-z][-a-z0-9]+\.)?[a-z][-a-z0-9]+\.[a-z]+(\.[a-z]{2,2})?)\/?[a-z0-9._\/~#&=;%+?-]+[a-z0-9\/#=?]{1,1})/is";
$text = preg_replace($urls, " <a href='$1'>$1</a>", $text);
// URLs without protocols
$text = preg_replace("/href=\"www/", "href=\"http://www", $text);
// Twitter usernames
$twitter = "/#([A-Za-z0-9_]+)/is";
$text = preg_replace ($twitter, " <a href='http://twitter.com/$1'>#$1</a>", $text);
// Twitter hashtags
$hashtag = "/#([A-Aa-z0-9_-]+)/is";
$text = preg_replace ($hashtag, " <a href='http://twitter.com/#!/search?q=%23$1'>#$1</a>", $text);
return $text;
}
You can use specific jQuery methods to make a JSONP request. There is basic $.ajax method and shorthand method $.getJSON which fits better for you. To control timeout of the request you can use timeout parameter. Request exceeded timeout can be processed using the error callback.
$.ajax(
dataType: 'jsonp',
url: 'http://search.twitter.com/search.json',
data: {
q: buildString,
rpp: 50
},
jsonpCallback: 'TweetTick',
timeout: 30000,
error: function(jqXHR, textStatus, errorThrown) {
if (textStatus == 'timeout') {
alert('timeout exceeded');
}
}
);
I have a link: Hello.
When someone clicks the link I'd like to check via JavaScript if the page the href-attribute points to exists or not. If the page exists the browser redirects to that page ("www.example.com" in this example) but if the page doesn't exist the browser should redirect to another URL.
It depends on whether the page exists on the same domain or not. If you're trying to determine if a page on an external domain exists, it won't work – browser security prevents cross-domain calls (the same-origin policy).
If it is on the same domain however, you can use jQuery like Buh Buh suggested. Although I'd recommend doing a HEAD-request instead of the GET-request the default $.ajax() method does – the $.ajax() method will download the entire page. Doing a HEAD request will only return the headers and indicate whether the page exists (response codes 200 - 299) or not (response codes 400 - 499). Example:
$.ajax({
type: 'HEAD',
url: 'http://yoursite.com/page.html',
success: function() {
// page exists
},
error: function() {
// page does not exist
}
});
See also: http://api.jquery.com/jQuery.ajax/
A pretty good work around is to proxy. If you don't have access to a server side you can use YQL. Visit: http://developer.yahoo.com/yql/console/
From there you can do something like: select * from htmlstring where url="http://google.com". You can use the "REST query" they have on that page as a starting point for your code.
Here's some code that would accept a full URL and use YQL to detect if that page exists:
function isURLReal(fullyQualifiedURL) {
var URL = encodeURIComponent(fullyQualifiedURL),
dfd = $.Deferred(),
checkURLPromise = $.getJSON('http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20htmlstring%20where%20url%3D%22' + URL + '%22&format=json');
checkURLPromise
.done(function(response) {
// results should be null if the page 404s or the domain doesn't work
if (response.query.results) {
dfd.resolve(true);
} else {
dfd.reject(false);
}
})
.fail(function() {
dfd.reject('failed');
});
return dfd.promise();
}
// usage
isURLReal('http://google.com')
.done(function(result) {
// yes, or request succeded
})
.fail(function(result) {
// no, or request failed
});
Update August 2nd, 2017
It looks like Yahoo deprecated "select * from html", although "select * from htmlstring" does work.
Based on the documentation for XMLHttpRequest:
function returnStatus(req, status) {
//console.log(req);
if(status == 200) {
console.log("The url is available");
// send an event
}
else {
console.log("The url returned status code " + status);
// send a different event
}
}
function fetchStatus(address) {
var client = new XMLHttpRequest();
client.onreadystatechange = function() {
// in case of network errors this might not give reliable results
if(this.readyState == 4)
returnStatus(this, this.status);
}
client.open("HEAD", address);
client.send();
}
fetchStatus("/");
This will however only work for URLs within the same domain as the current URL. Do you want to be able to ping external services? If so, you could create a simple script on the server which does your job for you, and use javascript to call it.
If it is in the same domain, you can make a head request with the xmlhttprequest object [ajax] and check the status code.
If it is in another domain, make an xmlhttprequest to the server and have it make the call to see if it is up.
why not just create a custom 404 handler on the web server? this is probably the more "good-bear" way to do this.
$.ajax({
url: "http://something/whatever.docx",
method: "HEAD",
statusCode: {
404: function () {
alert('not found');
},
200: function() {
alert("foundfile exists");
}
}
});
If you are happy to use jQuery you could do something like this.
When the page loads make an ajax call for each link. Then just replace the href of all the links which fail.
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js"></script>
<script type="text/javascript">
<!--
$.fn.checkPageExists = function(defaultUrl){
$.each(this, function(){
var $link = $(this);
$.ajax({
url: $link.attr("href"),
error: function(){
$link.attr("href", defaultUrl);
}
});
});
};
$(document).ready(function(){
$("a").checkPageExists("default.html");
});
//-->
</script>
You won't be able to use an ajax call to ping the website because of same-origin policy.
The best way to do it is to use an image and if you know the website you are calling has a favicon or some sort of icon to grab, you can just use an html image tag and use the onerror event.
Example:
function pingImgOnWebsite(url) {
var img = document.createElement('img');
img.style.visibility = 'hidden';
img.style.position = 'fixed';
img.src = url;
img.onerror = continueBtn; // What to do on error function
document.body.appendChild(img);
}
Another way to do this is is with PHP.
You could add
<?php
if (file_exists('/index.php'))
{
$url = '/index.php';
} else {
$url = '/notindex.php';
}
?>
And then
<a href="<?php echo $url; ?>Link</a>
I want to reload an image on a page if it has been updated on the server. In other questions it has been suggested to do something like
newImage.src = "http://localhost/image.jpg?" + new Date().getTime();
to force the image to be re-loaded, but that means that it will get downloaded again even if it really hasn't changed.
Is there any Javascript code that will cause a new request for the same image to be generated with a proper If-Modified-Since header so the image will only be downloaded if it has actually changed?
UPDATE: I'm still confused: if I just request the typical URL, I'll get the locally cached copy. (unless I make the server mark it as not cacheable, but I don't want to do that because the whole idea is to not re-download it unless it really changes.) if I change the URL, I'll always re-download, because the point of the new URL is to break the cache. So how do I get the in-between behavior I want, i.e. download the file only if it doesn't match the locally cached copy?
Javascript can't listen for an event on the server. Instead, you could employ some form of long-polling, or sequential calls to the server to see if the image has been changed.
You should have a look at the xhr.setRequestHeader() method. It's a method of any XMLHttpRequest object, and can be used to set headers on your Ajax queries. In jQuery, you can easily add a beforeSend property to your ajax object and set up some headers there.
That being said, caching with Ajax can be tricky. You might want to have a look at this thread on Google Groups, as there's a few issues involved with trying to override a browser's caching mechanisms. You'll need to ensure that your server is returning the proper cache control headers in order to be able to get something like this to work.
One way of doing this is to user server-sent events to have the server push a notification whenever the image has been changed. For this you need a server-side script that will periodically check for the image having been notified. The server-side script below ensures that the server sends an event at least once every (approximately) 60 seconds to prevent timeouts and the client-side HTML handles navigation away from and to the page:
sse.py
#!/usr/bin/env python3
import time
import os.path
print("Content-Type: text/event-stream\n\n", end="")
IMG_PATH = 'image.jpg'
modified_time = os.path.getmtime(IMG_PATH)
seconds_since_last_send = 0
while True:
time.sleep(1)
new_modified_time = os.path.getmtime(IMG_PATH)
if new_modified_time != modified_time:
modified_time = new_modified_time
print('data: changed\n\n', end="", flush=True)
seconds_since_last_send = 0
else:
seconds_since_last_send += 1
if seconds_since_last_send == 60:
print('data: keep-alive\n\n', end="", flush=True)
seconds_since_last_send = 0
And then your HTML would include some JavaScript code:
sse.html
<html>
<head>
<meta charset="UTF-8">
<title>Server-sent events demo</title>
</head>
<body>
<img id="img" src="image.jpg">
<script>
const img = document.getElementById('img');
let evtSource = null;
function setup_sse()
{
console.log('Creating new EventSource.');
evtSource = new EventSource('sse.py');
evtSource.onopen = function() {
console.log('Connection to server opened.');
};
// if we navigate away from this page:
window.onbeforeunload = function() {
console.log('Closing connection.');
evtSource.close();
evtSource = null;
};
evtSource.onmessage = function(e) {
if (e.data == 'changed')
img.src = 'image.jpg?version=' + new Date().getTime();
};
evtSource.onerror = function(err) {
console.error("EventSource failed:", err);
};
}
window.onload = function() {
// if we navigate back to this page:
window.onfocus = function() {
if (!evtSource)
setup_sse();
};
setup_sse(); // first time
};
</script>
</body>
</html>
Here am loading an image, tree.png, as binary data dynamically with AJAX and saving the Last-Modified header. Periodically (every 5 second in the code below). I issue another download request sending backup a If-Modified-Since header using the saved last-modified header. I check to see if data has been returned and re-create the image with the data if present:
<!doctype html>
<html>
<head>
<title>Test</title>
<script>
window.onload = function() {
let image = document.getElementById('img');
var lastModified = ''; // 'Sat, 11 Jun 2022 19:15:43 GMT'
function _arrayBufferToBase64(buffer) {
var binary = '';
var bytes = new Uint8Array(buffer);
var len = bytes.byteLength;
for (var i = 0; i < len; i++) {
binary += String.fromCharCode(bytes[i]);
}
return window.btoa( binary );
}
function loadImage()
{
var request = new XMLHttpRequest();
request.open("GET", "tree.png", true);
if (lastModified !== '')
request.setRequestHeader("If-Modified-Since", lastModified);
request.responseType = 'arraybuffer';
request.onload = function(/* oEvent */) {
lastModified = request.getResponseHeader('Last-Modified');
var response = request.response;
if (typeof response !== 'undefined' && response.byteLength !== 0) {
var encoded = _arrayBufferToBase64(response);
image.src = 'data:image/png;base64,' + encoded;
}
window.setTimeout(loadImage, 5000);
};
request.send();
}
loadImage();
};
</script>
</head>
<body>
<img id="img">
</body>
</html>
You can write a server side method which just returns last modified date of the image resource,
Then you just use polling to check for the modified date and then reload if modified date is greater than previous modified date.
pseudo code (ASP.NET)
//server side ajax method
[WebMethod]
public static string GetModifiedDate(string resource)
{
string path = HttpContext.Current.Server.MapPath("~" + resource);
FileInfo f = new FileInfo(path);
return f.LastWriteTimeUtc.ToString("yyyy-dd-MMTHH:mm:ss", CultureInfo.InvariantCulture);//2020-05-12T23:50:21
}
var pollingInterval = 5000;
function getPathFromUrl(url) {
return url.split(/[?#]/)[0];
}
function CheckIfChanged() {
$(".img").each(function (i, e) {
var $e = $(e);
var jqxhr = $.ajax({
type: "POST",
contentType: "application/json; charset=utf-8",
url: "/Default.aspx/GetModifiedDate",
data: "{'resource':'" + getPathFromUrl($e.attr("src")) + "'}"
}).done(function (data, textStatus, jqXHR) {
var dt = jqXHR.responseJSON.d;
var dtCurrent = $e.attr("data-lastwrite");
if (dtCurrent) {
var curDate = new Date(dtCurrent);
var dtLastWrite = new Date(dt);
//refresh if modified date is higher than current date
if (dtLastWrite > curDate) {
$e.attr("src", getPathFromUrl($e.attr("src")) + "?d=" + new Date());//fool browser with date querystring to reload image
}
}
$e.attr("data-lastwrite", dt);
});
}).promise().done(function () {
window.setTimeout(CheckIfChanged, pollingInterval);
});
}
$(document).ready(function () {
window.setTimeout(CheckIfChanged, pollingInterval);
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<img class="img" src="/img/rick.png" alt="rick" />
If you are going to check whether files has changed on the server you have to make http request from the server for the file time, because there is no other way for your check the file time once page get loaded to the browser.
So that time check script will like
filetimecheck.php
<?php
echo filemtime(string $filename);
?>
Then you can check the file time using your Javascript. BTW I have put jQuery $.get for check the file time.
dusplayimage.php
<img id="badge" src="image.jpg"> />
<script>
var image_time = <?php echo filemtime(string $filename); ?>;
var timerdelay = 5000;
function imageloadFunction(){
$.get("filetimecheck.php", function(data, status){
console.log("Data: " + data + "\nStatus: " + status);
if(image_time < parseInt(data)) {
document.getElementById('yourimage').src = "image.jpg?random="+new Date().getTime();
}
});
setTimeout(imageloadFunction, timerdelay);
}
imageloadFunction();
</script>
You will be using extra call to the server to check the file time which you can't avoid however you can use the time delay to fine-tune the polling time.
Yes, you can customize this behavior. Even with virtually no change to your client code.
So, you will need a ServiceWorker (caniuse 96.59%).
ServiceWorker can proxy your http requests. Also, ServiceWorker has already built-in storage for the cache. If you have not worked with ServiceWorker, then you need to study it in detail.
The idea is the following:
When requesting a picture (in fact, any file), check the cache.
If there is no such picture in the cache, send a request and fill the cache storage with the date of the request and the file.
If the cache contains the required file, then send only the date and path of the file to the special API to the server.
The API returns either the file and modification date at once (if the file was updated), or the response that the file has not changed {"changed": false}.
Then, based on the response, the worker either writes a new file to the cache and resolves the request with the new file, or resolves the request with the old file from the cache.
Here is an example code (not working, but for understanding)
s-worker.js
self.addEventListener('fetch', (event) => {
if (event.request.method !== 'GET') return;
event.respondWith(
(async function () {
const cache = await caches.open('dynamic-v1');
const cachedResponse = await cache.match(event.request);
if (cachedResponse) {
// check if a file on the server has changed
const isChanged = await fetch('...');
if (isChanged) {
// give file, and in the background write to the cache
} else {
// return data
}
return cachedResponse;
} else {
// request data, send from the worker and write to the cache in the background
}
})()
);
});
In any case, look for "ways to cache statics using ServiceWorker" and change the examples for yourself.
WARNING this solution is like taking a hammer to crush a fly
You can use sockets.io to pull information to browser.
In this case you need to monitor image file changes on the server side, and then if change occur emit an event to indicate the file change.
On client (browser) side listen to the event and then then refresh image each time you get the event.
set your image source in a data-src property,
and use javascript to periodicaly set it to the src attribute of that image with a anchor (#) the anchor tag in the url isn't send to the server.
Your webserver (apache / nginx) should respond with a HTTP 304 if the image wasn't changed, or a 200 OK with the new image in the body, if it was
setInterval(function(){
l= document.getElementById('logo');
l.src = l.dataset.src+'#'+ new Date().getTime();
},1000);
<img id="logo" alt="awesome-logo" data-src="https://upload.wikimedia.org/wikipedia/commons/1/11/Test-Logo.svg" />
EDIT
Crhome ignores http cache-control headers, for subsequent image reloads.
but the fetch api woks as expected
fetch('https://upload.wikimedia.org/wikipedia/commons/1/11/Test-Logo.svg', { cache: "no-cache" }).then(console.log);
the no-cache instructs the browser to always revalidate with the server, and if the server responds with 304, use the local cached version.