- From: Jonas Sicking <jonas@sicking.cc>
- Date: Fri, 16 Jan 2009 19:04:19 -0800
Hi All, Not sure if I should be posting this to the whatwg list or the webapps list, given that the spec is in process of transitioning between the two groups. So I'm posting to both in the hope that this thread won't generate too much related traffic. So please stay on topic :) Currently the webapps spec define that the onerror property should start out as undefined, rather than other onX properties which start out as null. The reason for this is parity with the window object where the onerror property behaves the same. However there is very little parity anyway between the window onerror and the worker onerror. The former isn't a normal event handler but rather a special function that receives 3 arguments and returns a special value to suppress the error. The latter is a normal event handler which receives an error event and suppresses the error by calling .preventDefault() on the event. Further, the fact that onerror is undefined at the start is to prevent breaking existing scripts, of which there are none for workers. So I think it'd be nicer to have parity with other onX properties, than to have parity on this one aspect with window.onerror. Second, does the spec define what happens if an error is thrown from 'error' event handler? We have found it useful to prevent firing an 'error' event same scope again. We'll still fire an error event in the parent scope worker, but we don't call onerror again in the same scope. Otherwise the risk of infinite recursion is very big. While we have other things that prevents such runaway recursions from causing the crash, each recursion would cause onerror to be called on the parent which means that a torrent of error events would be fired on the parent. The result is that the following script alerts twice, first 'inside onerror' and then 'throwing': main.html: <script> w = new Worker('w.js'); c = 1; w.onerror = function(e) { alert(e.message); }; </script> w.js: function onerror(e) { throw "inside onerror"; } throw "throwing"; / Jonas
Received on Friday, 16 January 2009 19:04:19 UTC