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I have a script which can be run either directly or, when available in the browser, as a Web Worker. I'd like to run a portion of this script only when run as a worker; so my question is, how can a script identify itself as being run this way?
I can't see anything in the spec that would allow this to happen; am I missing something obvious?
265
In the following :
<html>
<head>
<title>Worker</title>
</head>
<body>
</body>
<script >
var w = new Worker ('worker.js');
w.onmessage = function (e) {
document.body.innerHTML += '<br>' + 'WORKER : ' + e.data;
};
</script>
<script src='worker.js'></script>
</html>
worker.js is invoked both as a script and as a worker.
worker.js contains :
var msg = 'postMessage is ' + postMessage.toString () +
', self.constructor is ' + self.constructor;
try {
postMessage (msg);
} catch (e) {
document.body.innerHTML += '<br>SCRIPT : ' + msg;
}
In the worker environment, the postMessage succeeds, in the script environment it fails because either it is undefined or, in a browser, it requires a second argument.
Output is :
chrome :
SCRIPT : postMessage is function () { [native code] }, self.constructor is function DOMWindow() { [native code] }
WORKER : postMessage is function postMessage() { [native code] }, self.constructor is function DedicatedWorkerContext() { [native code] }
firefox :
SCRIPT : postMessage is function postMessage() { [native code] }, self.constructor is [object Window]
WORKER : postMessage is function postMessage() { [native code] }, self.constructor is function DedicatedWorkerGlobalScope() { [native code] }
opera:
WORKER : postMessage is function postMessage() { [native code] }, self.constructor is function Object() { [native code] }
SCRIPT : postMessage is function postMessage() { [native code] }, self.constructor is function Object() { [native code] }
All under Ubuntu.
136
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