How to save the JavaScript errors in file

Question

Need a solution for saving log of JavaScript errors. For automated testing any site with support popular web browsers (IE, FF, Chrome).

Answer 1

Most practical method is to look for an event onerror. try-catch is the best method, but you should know where in your code is possible to appear an error.

Here alert is used. It can be replaced with an ajax call to some server-side script/app which will be responsible for the database logging of the message. JavaScript by itself can`t access any file-system - server's or user's. This will only send info about the error. demo

window.onerror = function (msg, url, num) {
    alert("Error: " + msg + "\nURL: " + url + "\nLine: " + num);
    return true;
};
JS-made-poo();

Internet Explorer uses ActiveX, which may be useful in some kind of a logging application. But the user probably will receive a warning when the ActiveX is fired.