How to Log Javascript Errors in C#

This code shows how to handle a JavaScript error by posting the details back to the server to be logged. This code can be wired up to use any logging system.

The errors.js file establishes a handler for window.onerror to call the handleError function. The handleError function creates a web request (using the createHttpRequest function in httpRequests.js) and posts the error details back to LogJavascriptError.aspx. The LogJavascriptError.aspx file then logs the details to the file.

var applicationPath = '';

function handleError(msg, srcUrl, line){

    var receiveReq = createHttpRequest();

    var url = applicationPath + '/Admin/LogJavascriptError.aspx';

    var data  = "ErrorData=" + msg + "&SourcePage=" + srcUrl + "&Line=" + line;

    receiveReq.open("POST", url, true);

    receiveReq.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    receiveReq.setRequestHeader("Content-length", data.length);
    receiveReq.setRequestHeader("Connection", "close");

    receiveReq.send(data);
}

window.onerror=handleError;

http://code.google.com/p/sitestarter/source/browse/trunk/Src/App/WWW/js/errors.js[^]

function createHttpRequest() {
    if (window.XMLHttpRequest) {
        return new XMLHttpRequest(); //Not IE
    } else if(window.ActiveXObject) {
        return new ActiveXObject("Microsoft.XMLHTTP"); //IE
    } else {
        alert("Your browser doesn't support the XmlHttpRequest object.  Please upgrade to Firefox.");
    }
}

http://code.google.com/p/sitestarter/source/browse/trunk/Src/App/WWW/js/httpRequests.js[^]

string errorData = Request.Form["ErrorData"];
string sourcePage = Request.Form["SourcePage"];
string line = Request.Form["Line"];

string full = "Javascript error: " + errorData + Environment.NewLine + 
              "Location: " + sourcePage + ", line " + line;

LogWriter.Error(full);

Response.Write("Done");

http://code.google.com/p/sitestarter/source/browse/trunk/Src/App/WWW/Admin/LogJavascriptError.aspx[^]