/* 
JavaScript Error Trapping and Logging 

This library module enables suppression of 
JavaScript errors in a way that allows errors 
to be hidden from view, logged to a server 
log file for further review, and optionally 
displayed in the window.status area if desired. 

Source: Webmonkey Code Library 
(http://www.hotwired.com/webmonkey/javascript/code_library/) 

Author: Patrick Corcoran 
Author email: patrick@taylor.org 
*/ 

if ( 1 ) { 

trapErrors = true; 
// Setting this to false will turn off JS error suppression, 
// setting the browser to its normal behavior. 
// Useful for debugging during development. 

logErrors = true; 
// Setting this to false will stop errors from being logged. 
// Useful when working offline or without CGI. 

showErrorAsStatusMessage = true; 
// Setting this to true will cause the browser to display 
// the error message as the window.defaultStatus text, 
// resulting in a quieter, but not invisible, error message. 
// Sometimes this can be a more pleasant way to debug JavaScript. 

} 
else { 
trapErrors = false; 
logErrors = false; 
showErrorAsStatusMessage = false; 
} 

logNumErrors = 3; 
// Number of JS errors per page to enter into log before calling it quits. 
// Large values aren't recommended ... if you're getting a lot 
// of errors per pageview, then you're probably in a nasty loop. 

logScriptLoc = 'javas_error_log.php'; 
// The script must reside within the htdocs tree 
// or in a server-aliased directory like /cgi-bin, 
// since the error message is sent via HTTP. 

scriptName = "JS Err Log"; 
// Optional: This can be any string of text used to identify the script. 

MSIE = (navigator.userAgent.indexOf('MSIE') > -1) ? ( true ) : ( false ); 
// Is this browser a Microsoft Internet Explorer browser? 

if (!MSIE) { originalErrorHandler = window.onerror; } 
// Read and store value of current window.onerror property for later restoring. 
// But exclude MSIE because it won't allow us to read the window.onerror property. 

originalDefaultStatus = window.defaultStatus; 
// Read and store value of current window.defaultStatus property for later restoring. 

numErrorEvents = 0; 
// Number of Errors we've experienced so far for this pageview. 

function handleErrors(msg, line) { 

if (logErrors || showErrorAsStatusMessage) { 

if (numErrorEvents < logNumErrors) { 

errImage = new Array(logNumErrors); 
// This will hold all of our Image() objects we will create 
// to pass error data to the server. 

d = new Date(); 
// We append a new Date() object to the end of every GET string 
// to ensure that the URL is always unique, and therefore not 
// subject to the disk cache frustrations of MSIE. 

if (MSIE) { 
// window.onerror in MSIE doesn't pass msg, line values 
// automatically like Netscape does, so we must approximate them. 
msg = 'Unspecified JS Error'; 
line = 'MSIE'; 
} 
else { 
line = 'line ' + line; 
} 

if (logErrors) { 

errLogEntry = logScriptLoc + '?msg=' + escape(msg) + '&line=' + escape(line) + '&d=' + escape(d); 
// Build a GET string from the data we have pieced together about the error event. 

errImage[numErrorEvents] = new Image(); 
errImage[numErrorEvents].src = errLogEntry; 
// The Image() object is essentially the only Object 
// in NS3, NS4, and MSIE that can have its URL refreshed 
// without reloading the page, so we use it as a background data 
// carrier for client->server communication. We set the new URL equal 
// to our GET string, which will get parsed by the CGI on the server. 
// The CGI will return empty/garbage data, but we don't care, 
// since the image we're loading here isn't for display. 
} 

if (showErrorAsStatusMessage) { 
window.defaultStatus = 'JavaScript Error: ' + msg + ' in ' + line; 
} 

numErrorEvents++; 
} 
} 

return trapErrors; 
} 

function restoreWindowToPreviousState() { 
// Set window.onerror and window.defaultStatus 
// to their initial state when leaving the page. 
if (!MSIE) { 
window.onerror = originalErrorHandler; 
} 
window.defaultStatus = originalDefaultStatus; 
} 

window.onUnload = restoreWindowToPreviousState; 

window.onerror = handleErrors;