Simple long polling example with JavaScript and jQuery - Stack Overflow

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I'm trying to create a real-time website analytics dashboard which creates an open HTTP connection to the server using jQuery/JavaScript asynchronously to poll the server for updates to the data as and when they occur.

The obvious start for this would be to use an XMLHttpRequest object or jQuery's $.ajax method to send a GET or POST request to the server asynchronously requesting some data.

However, beyond sending one request at a time using a setInterval method every 30 seconds I am not sure how to make the connection to the server persistent. Basically, I only want to send one http request and ensure the connection to the server stays open for polling!

My example code with setInterval is as follows:

<div id="analytics"></div>
<script>
var analytics = document.getElementById('analytics');
setInterval(function(){
    $.ajax({ url: "/", success: function(data){
        analytics.innerHTML = data;
    }, dataType: "json"});
}, 30000);
</script>

I'm trying to create a real-time website analytics dashboard which creates an open HTTP connection to the server using jQuery/JavaScript asynchronously to poll the server for updates to the data as and when they occur.

The obvious start for this would be to use an XMLHttpRequest object or jQuery's $.ajax method to send a GET or POST request to the server asynchronously requesting some data.

However, beyond sending one request at a time using a setInterval method every 30 seconds I am not sure how to make the connection to the server persistent. Basically, I only want to send one http request and ensure the connection to the server stays open for polling!

My example code with setInterval is as follows:

<div id="analytics"></div>
<script>
var analytics = document.getElementById('analytics');
setInterval(function(){
    $.ajax({ url: "http://server./", success: function(data){
        analytics.innerHTML = data;
    }, dataType: "json"});
}, 30000);
</script>

• javascript
• jquery
• asynchronous

Share Improve this question Follow asked Dec 25, 2012 at 1:31 technojastechnojas 26911 gold badge22 silver badges77 bronze badges 8

• 1 is there any reason why you need to send only one http request? you may want to look into websockets if you want a persistent connection. – kennypu Commented Dec 25, 2012 at 1:35
• http doesn't work that way – charlietfl Commented Dec 25, 2012 at 1:38
• I guess two reasons I want persistence: (1) it will ensure my updates are more real-time and (2) I think its better performance i.e. less thrashing the server with multiple requests? – technojas Commented Dec 25, 2012 at 1:38
• @technojas as charlietfl said, http isn't like tcp connections etc. and it doesn't work that way. Use websockets if you must have a real connection. on the other hand, I don't think there is anything wrong with sending an ajax request frequently, especially every 30 seconds. – kennypu Commented Dec 25, 2012 at 1:39
• 2 if you are doing long polling, you will need special care on your server side (non-blocking i/o), look at socket.io, or research et projects for your server – jermel Commented Dec 25, 2012 at 1:44

 |  Show 3 more ments

1 Answer 1

Sorted by: Reset to default 12

After searching online, this was the answer I was looking for which doesn't use sockets.io nor WebSockets but does use jQuery by taking advantage of its plete method to create an artificial loop:

<div id="analytics"></div>
<script>
var analytics = document.getElementById('analytics');
(function poll(){
    $.ajax({ url: "server", success: function(data){
        analytics.innerHTML = data;
    }, dataType: "json", plete: poll, timeout: 30000 });
})();
</script>

Source is Tian Davis from Technoctave: http://techoctave./c7/posts/60-simple-long-polling-example-with-javascript-and-jquery

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