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Using the onerror event is the old standard
solution to catch errors in a web page.
The onerror Event
We have just explained how to use the try...catch statement
to catch errors in a web page. Now we are going to explain how
to use the onerror event for the same purpose.
The onerror event is fired whenever there is a script error
in the page.
To use the onerror event, you must create a function to
handle the errors. Then you call the function with the onerror
event handler. The event handler is called with three arguments:
msg (error message), url (the url of the page that caused the
error) and line (the line where the error occurred).
Syntax
onerror=handleErr
function handleErr(msg,url,l)
{
//Handle the error here
return true or false
}
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The value returned by onerror determines whether the browser
displays a standard error message. If you return false, the
browser displays the standard error message in the JavaScript
console. If you return true, the browser does not display the
standard error message.
Example
The following example shows how to catch the error with the
onerror event:
<html>
<head>
<script type="text/javascript">
onerror=handleErr
var txt=""
function handleErr(msg,url,l)
{
txt="There was an error on this page.\n\n"
txt+="Error: " + msg + "\n"
txt+="URL: " + url + "\n"
txt+="Line: " + l + "\n\n"
txt+="Click OK to continue.\n\n"
alert(txt)
return true
}
function message()
{
adddlert("Welcome guest!")
}
</script>
</head>
<body>
<input type="button" value="View message" onclick="message()" />
</body>
</html>
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