Prototype JS swallows errors in dom:loaded, and ajax callbacks?
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by WishCow
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Published on 2010-03-23T21:47:47Z
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2010/03/23
21:53 UTC
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I can't figure out why prototype suppressess the error messages in the dom:loaded event, and in AJAX handlers.
Given the following piece of HTML:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Conforming XHTML 1.1 Template</title>
<script type="text/javascript" src="prototype.js"></script>
<script type="text/javascript">
document.observe('dom:loaded', function() {
console.log('domready');
console.log(idontexist);
});
</script>
</head>
<body>
</body>
</html>
The domready event fires, I see the log in the console, but there is no indication of any errors whatsoever. If you move the console.log(idontexist); line out of the handler, you get the
idontexist is not defined
error in the console.
I find it a little weird, that in other event handlers, like 'click', you get the error message, it seems that it's only the dom:loaded that has this problem.
The same goes for AJAX handlers:
new Ajax.Request('/', {
method: 'get',
onComplete: function(r) {
console.log('xhr complete');
alert(youwontseeme);
}
});
You won't see any errors. This is with prototype.js 1.6.1, and I can't find any indication of this behavior in the docs, nor a way to enable error reporting in these handlers.
I have tried stepping through the code with FireBug's debugger, and it seems to jump to a function on line 53 named K, when it encounters the missing variable in the dom:loaded handler:
K: function(x) { return x }
But how? Why? When? I can't see any try/catch block there, how does the program flow end up there?
I know that I can make the errors visible by packing my dom:ready handler(s) in try/catch blocks, but that's not a very comfortable option. Same goes for registering a global onException handler for the AJAX calls.
Why does it even suppress the errors? Did someone encounter this before?
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