Catch JS errors on web page or web applications

Here is a code snippet to catch the script errors which could be generated on your web application.

It should be such that when its development environment, it must show a alert message and when its production environment, it sends a email or logs into a table.

//
// Traps all js errors
function catchJSError(a,b,c,d) {
//var lines= document.body.innerHTML.split('\n');
//var errorline = lines[c];


// Get error line
var source = document.body.innerHTML;
source = source.split("\n");

var bugline = ((c-1) + ":" + source[c-1] + "\n" +
(c) + ":" + source[c] + "\n" +
(c+1) + ":" + source[c+1] + "\n"
);



var bug = "<b>JS Error:</b> " + a +
"<BR><b>Error in the file:</b> " + b +
"<BR><b>On Line:</b> " + c +
"<BR><b>Character:</b> " + (isIE==true)?event.errorCharacter:"0" +
"<BR><b>Window Title:</b> " + document.title +
"<BR><b>Error Type:</b> " + (isIE==true)?e.errorCode:"0" + "<BR><BR>";


var file = window.location.pathname;
file = file.substring (file.lastIndexOf("/"));

var subject = escape("JS error on " + window.location.host + " : " + file);

var live_servers = "prod.checkingserver.com";

// Send email if a live server
if (live_servers.indexOf(document.domain)>=0) {

sendAjaxRequest("reportJSError.do", "subject="+subject+"&bug="+ escape(bug) );
}
else
alert(bug.replace(/<b>/g,"").replace(/<\/B>/g,"").replace(/<BR>/g,"\\n"));


return false;
}
window.onerror=catchJSError;