simple window.onerror handler

errorhandler.js

function errorHandler(msg, url, line, column, err) {
    // firefox bug to watch for 5 arg error handler
    // https://bugzilla.mozilla.org/show_bug.cgi?id=630464

    /*
     * most browsers don't give column number,
     * but chrome can do it sometimes
     */
    if(typeof column == "object") {
      err = column;
    }

    if(typeof column !== "number") {
      column = undefined;
    }

    var event = {
      event: "error",
      name:  "jsError",
      data: {
        url: url || window.location.href,
        msg: (err && err.message) || msg,
        line: line,
        column: column,
        useragent: navigator.userAgent,
        stack: err && err.stack
      }
    };
    
    // Here you'd have to use whatever you have
    // to post to your logging server
    writeToMyErrorLogger(event);
}

window.onError = errorHandler;

/*
Important configuration instructions:
To get good error messages, including stacks and so
your JS files from CDN needs to be served with an appropirate Access-Control-Allow-Origin header,
AND you need to use the attribtue crossorigin="anonymous" on all the script tags loading scripts
that should be reported

if you don't use CDN you don't need to care
*/