Thursday, May 27th, 2010
Chrome supporting EventSource for server push, and richer Worker API
Category: Chrome
First, he uncovers new support for the EventSource API that allows for simple server push of DOM events as shown in this simple client and server pairing:
- document.addEventListener('DOMContentLoaded', function () {
- var eventSrc = new EventSource('events.php');
- eventSrc.addEventListener('open', function (event) {
- console.log(event.type);
- });
- eventSrc.addEventListener('message', function (event) {
- console.log(event.type);
- console.log(event.data);
- });
- }, false);
- < ?php
- header("Content-Type: text/event-stream\n\n");
- // despite not having the while(true){}
- // this seems to repeat pushing messages to the client
- echo 'data: ' . time() . "\n";
Then, he finds out that the Web Worker API now supports complex messages, so you can postMessage more than Strings. Send over objects and Arrays with ease:
- // TEST ANOTHER THREAD SAFE OBJECT ARG
- var obj = new Object();
- obj.isArray = [ 1,2,3,4,5 ];
- obj.isString = 'Foo bar baz',
- obj.resultOf = (function () {
- return 'returned from self executing function';
- })();
- worker.postMessage(obj);
- // TEST STRING ARG
- worker.postMessage('Hello Worker Process');
- // TEST ARRAY ARG
- worker.postMessage([ 1, 2, 3, 4 ]);
- // TEST BOOLEAN ARG
- worker.postMessage(false);
Related Content:
3.5 rating from 2 votes
Several WebWorker-related projects worth checking out (some mentioned on Ajaxian before):
1) Metaworker – mapreduce with workers – http://bit.ly/7oTuS5
2) Pmrpc – RPC/pubsub communication with workers and windows/iframes – http://bit.ly/JMtkm (I’m one of the developers)
3) jQuery Hive – creating and managing web workers across implementations – http://bit.ly/c5ihqm
4) Javascript Enumerable.Map() with WebWorkers – http://bit.ly/cY8M9P
I’ve made an example on which you can see Server-Sent Event in action using mentioned here Chrome 6, Safari 5 or Opera 9 – http://sapid.sourceforge.net/ssetest/
Just for a calcification on the comment within the events.php file that reads:
// despite not having the while(true){}
// this seems to repeat pushing messages to the client
You don’t need a while(true) block at all, because the user agent (browser) is going to ask for updates from that file about every 3 seconds unless you ask for different time, or the events.php returns a non 200 response from the server.
When you setup var eventSrc = new EventSource(‘events.php’); You told the browser that you want to check this file for updates. So the browser will request that file automatically.
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The second thing that I would like to fix is the content-type of the event.php file. It should be header(“Content-Type: text/event-stream”); No NN at the end.
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The third and final issue I see is that echo ‘data: ‘ . time() . “n”; should read echo ‘data: ‘ . time() . “\n\n”; Like headers, you one a single \n to end the line, and you use \n\n to end the section.