问题
I am trying to implement Server-Sent Events (SSE) inside a SharedWorker.
The implementation is working with no problems in Google Chrome. However, it does not work in FireFox at all.
When I try get it to work in FireFox I get this error in the console.
error {
target: SharedWorker,
isTrusted: true,
message: "ReferenceError: EventSource is not defined",
filename: "https://example.com/add-ons/icws/js/worker.js",
lineno: 28,
colno: 0,
currentTarget: SharedWorker,
eventPhase: 2,
bubbles: false,
cancelable: true,
defaultPrevented: false
}
How can I make EventSource available inside the SharedWorker?
This is how I establish connection the the SharedWorker
$(window).load(function(){
//establish connection to the shared worker
var worker = new SharedWorker("/add-ons/icws/js/worker.js" );
//listen for a message send from the worker
worker.port.addEventListener("message",
function(event) {
console.log( Math.random() );
processServerData(event.data);
}
, false
);
worker.onerror = function(event){
console.log(event);
};
//start the connection to the shared worker
worker.port.start();
});
This is my worker script
var clients = new Array();
readNewMessages();
//runs only when a new connection starts
onconnect = function(event) {
var port = event.ports[0];
clients.push(port);
port.start();
//implement a channel for a communication between the connecter and the SharedWorker
port.addEventListener("message",
function(event) {
replyToClientMessage(event, port);
} , false
);
}
//reply to any message sent to the SharedWorker
replyToClientMessage = function (event, port) {
port.postMessage(event.data);
}
//runs every time and post the message to all the connected client
function readNewMessages(){
var serv = new EventSource('/add-ons/icws/poll.php');
serv.addEventListener("getMessagingQueue", function(event) {
var queue = JSON.parse(event.data);
notifyAllPorts(queue);
}, false);
}
//check all open clients and post a message to each
function notifyAllPorts(msg){
var len = clients.length;
var port;
for(i = 0; i < len; i++) {
port = clients[i];
port.postMessage(msg);
}
}
While searching for a solution, I learned that EventSource is not part of SharedWorkerGlobalScope
I tried to change my worker code to this, but still that did not work
var serv = new self.EventSource('/add-ons/icws/poll.php');
var clients = new Array();
readNewMessages();
//runs only when a new connection starts
onconnect = function(event) {
var port = event.ports[0];
clients.push(port);
port.start();
//implement a channel for a communication between the connecter and the SharedWorker
port.addEventListener("message",
function(event) {
replyToClientMessage(event, port);
} , false
);
}
//reply to any message sent to the SharedWorker with the same message but add the phrase "SharedWorker Said: " to it
replyToClientMessage = function (event, port) {
port.postMessage(event.data);
}
//runs every time and post the message to all the connected client
function readNewMessages(){
serv.addEventListener("getMessagingQueue", function(event) {
var queue = JSON.parse(event.data);
notifyAllPorts(queue);
}, false);
}
//check all open clients and post a message to each
function notifyAllPorts(msg){
var len = clients.length;
var port;
for(i = 0; i < len; i++) {
port = clients[i];
port.postMessage(msg);
}
}
How can fix this problem?
回答1:
Why FF would let you have a WebSocket in a Worker but not an EventSource I'm not sure, but it does give you all of the tools to make a good polyfill (stick it in the top of your SharedWorker script):
//FF only; some missing functionality, but handles the essentials
//most of what's missing can be added if you have the motivation
(function(global) {
if ('EventSource' in global)
return;
function EventSource(url) {
if (!(this instanceof EventSource))
return new EventSource(url);
this.url = url;
var self = this;
var listeners = {};
self.addEventListener = function(type, handler) {
if (!listeners[type]) {
listeners[type] = new Set();
}
listeners[type].add(handler);
};
self.removeEventListener = function(type, handler) {
if (listeners[type]) {
listeners[type].delete(handler);
}
};
self.dispatchEvent = function(event) {
if (listeners[event.type]) {
listeners[event.type].forEach(function(handler) {
setTimeout(function() {
switch (typeof(handler)) {
case 'object':
handler.handleEvent(event);
break;
case 'function':
handler(event);
break;
}
});
});
}
if (typeof(self['on' + event.type.toLowerCase()]) == 'function') {
setTimeout(function() {
self['on' + event.type.toLowerCase()](event);
});
}
};
var buffer = '';
//if you want to handle other prefixes, you'll need to tweak these
var msgRE = /^(?:data: .*\n)*\n/;
var dataRE = /^data: (.*)$/;
function _parse() {
while (msgRE.test(buffer)) {
var msg = msgRE.exec(buffer)[0]; //msg now contains a single raw message
var data = null;
var lines = msg.split("\n").slice(0, -2); //remove last 2 newlines
if (lines.length) {
data = '';
lines.forEach(function(line) {
data += dataRE.exec(line)[1];
});
}
var event = new MessageEvent('message', { 'data' : data, 'origin' : url });
self.dispatchEvent(event);
buffer = buffer.substr(msg.length);
}
}
var xhr = new XMLHttpRequest();
xhr.open('GET', url, true);
xhr.responseType = 'moz-chunked-text'; //FF only
xhr.setRequestHeader('Accept', 'text/event-stream');
xhr.onprogress = function() {
if (xhr.response !== null) {
buffer += xhr.response;
}
_parse();
};
xhr.onreadystatechange = function() {
switch (xhr.readyState) {
case XMLHttpRequest.HEADERS_RECEIVED:
if (xhr.status == 200) {
self.readyState = EventSource.OPEN;
break;
} //else
console.error("EventSource: " + url + " = " + xhr.statusText);
//fallthrough
case XMLHttpRequest.DONE:
self.readyState = EventSource.CLOSED;
break;
default:
break;
}
};
xhr.send();
Object.defineProperty(this, 'close', { 'value' : function() {
xhr.abort();
}});
return this;
}
Object.defineProperties(EventSource, {
'CONNECTING' : { 'value' : 0, 'enumerable' : true },
'OPEN' : { 'value' : 1, 'enumerable' : true },
'CLOSED' : { 'value' : 2, 'enumerable' : true },
});
EventSource.prototype = Object.create(EventTarget.prototype);
Object.defineProperties(EventSource.prototype, {
'constructor' : { 'value' : EventSource },
'readyState' : { 'value' : 0, 'writable' : true, 'enumerable' : true },
'withCredentials' : { 'value' : false, 'enumerable' : true }, //not supported
'onopen' : { 'writable' : true },
'onmessage' : { 'writable' : true },
'onerror' : { 'writable' : true },
'close' : { 'value' : function() { }, 'configurable' : true, 'enumerable' : true }
});
global.EventSource = EventSource;
})(this);
You can find more complete polyfills here and here. I needed one that works with a real-time uncached stream (if you aren't connected to the stream when the event happens, it's gone); this is what I came up with. The main difference is the moz-chunked-text responseType, which gives you uncached stream access in the progress event. Enjoy ;-)
来源：https://stackoverflow.com/questions/32321295/how-to-make-eventsource-available-inside-sharedworker-in-firefox