<script type="text/javascript">
window.onerror = function(msg, url, line, col, error) {
// Note that col & error are new to the HTML 5 spec and may not be
// supported in every browser. It worked for me in Chrome.
var extra = !col ? '' : '\ncolumn: ' + col;
extra += !error ? '' : '\nerror: ' + error;
// You can view the information in an alert to see things working like this:
alert("Error: " + msg + "\nurl: " + url + "\nline: " + line + extra);
// TODO: Report this error via ajax so you can keep track
// of what pages have JS issues
var suppressErrorAlert = true;
// If you return true, then error alerts (like in older versions of
// Internet Explorer) will be suppressed.
return suppressErrorAlert;
};
</script>
// Only Chrome & Opera pass the error object.
window.onerror = function (message, file, line, col, error) {
console.log(message, "from", error.stack);
// You can send data to your server
// sendError(data);
};
// Only Chrome & Opera have an error attribute on the event.
window.addEventListener("error", function (e) {
console.log(e.error.message, "from", e.error.stack);
// You can send data to your server
// sendError(data);
})
function wrap(func) {
// Ensure we only wrap the function once.
if (!func._wrapped) {
func._wrapped = function () {
try{
func.apply(this, arguments);
} catch(e) {
console.log(e.message, "from", e.stack);
// You can send data to your server
// sendError(data);
throw e;
}
}
}
return func._wrapped;
};
(function(){
/**
* Capture error data for debugging in web console.
*/
var captures = [];
/**
* Wait until `window.onload`, so any external scripts
* you might load have a chance to set their own error handlers,
* which we don't want to override.
*/
window.addEventListener('load', onload);
/**
* Custom global function to standardize
* window.onerror so it works like you'd think.
*
* @see http://www.quirksmode.org/dom/events/error.html
*/
window.onanyerror = window.onanyerror || onanyerrorx;
/**
* Hook up all error handlers after window loads.
*/
function onload() {
handleGlobal();
handleXMLHttp();
handleImage();
handleScript();
handleEvents();
}
/**
* Handle global window events.
*/
function handleGlobal() {
var onerrorx = window.onerror;
window.addEventListener('error', onerror);
function onerror(msg, url, line, col, error) {
window.onanyerror.apply(this, arguments);
if (onerrorx) return onerrorx.apply(null, arguments);
}
}
/**
* Handle ajax request errors.
*/
function handleXMLHttp() {
var sendx = XMLHttpRequest.prototype.send;
window.XMLHttpRequest.prototype.send = function(){
handleAsync(this);
return sendx.apply(this, arguments);
};
}
/**
* Handle image errors.
*/
function handleImage() {
var ImageOriginal = window.Image;
window.Image = ImageOverride;
/**
* New `Image` constructor. Might cause some problems,
* but not sure yet. This is at least a start, and works on chrome.
*/
function ImageOverride() {
var img = new ImageOriginal;
onnext(function(){ handleAsync(img); });
return img;
}
}
/**
* Handle script errors.
*/
function handleScript() {
var HTMLScriptElementOriginal = window.HTMLScriptElement;
window.HTMLScriptElement = HTMLScriptElementOverride;
/**
* New `HTMLScriptElement` constructor.
*
* Allows us to globally override onload.
* Not ideal to override stuff, but it helps with debugging.
*/
function HTMLScriptElementOverride() {
var script = new HTMLScriptElement;
onnext(function(){ handleAsync(script); });
return script;
}
}
/**
* Handle errors in events.
*
* @see http://stackoverflow.com/questions/951791/javascript-global-error-handling/31750604#31750604
*/
function handleEvents() {
var addEventListenerx = window.EventTarget.prototype.addEventListener;
window.EventTarget.prototype.addEventListener = addEventListener;
var removeEventListenerx = window.EventTarget.prototype.removeEventListener;
window.EventTarget.prototype.removeEventListener = removeEventListener;
function addEventListener(event, handler, bubble) {
var handlerx = wrap(handler);
return addEventListenerx.call(this, event, handlerx, bubble);
}
function removeEventListener(event, handler, bubble) {
handler = handler._witherror || handler;
removeEventListenerx.call(this, event, handler, bubble);
}
function wrap(fn) {
fn._witherror = witherror;
function witherror() {
try {
fn.apply(this, arguments);
} catch(e) {
window.onanyerror.apply(this, e);
throw e;
}
}
return fn;
}
}
/**
* Handle image/ajax request errors generically.
*/
function handleAsync(obj) {
var onerrorx = obj.onerror;
obj.onerror = onerror;
var onabortx = obj.onabort;
obj.onabort = onabort;
var onloadx = obj.onload;
obj.onload = onload;
/**
* Handle `onerror`.
*/
function onerror(error) {
window.onanyerror.call(this, error);
if (onerrorx) return onerrorx.apply(this, arguments);
};
/**
* Handle `onabort`.
*/
function onabort(error) {
window.onanyerror.call(this, error);
if (onabortx) return onabortx.apply(this, arguments);
};
/**
* Handle `onload`.
*
* For images, you can get a 403 response error,
* but this isn't triggered as a global on error.
* This sort of standardizes it.
*
* "there is no way to get the HTTP status from a
* request made by an img tag in JavaScript."
* @see http://stackoverflow.com/questions/8108636/how-to-get-http-status-code-of-img-tags/8108646#8108646
*/
function onload(request) {
if (request.status && request.status >= 400) {
window.onanyerror.call(this, request);
}
if (onloadx) return onloadx.apply(this, arguments);
}
}
/**
* Generic error handler.
*
* This shows the basic implementation,
* which you could override in your app.
*/
function onanyerrorx(entity) {
var display = entity;
// ajax request
if (entity instanceof XMLHttpRequest) {
// 400: http://example.com/image.png
display = entity.status + ' ' + entity.responseURL;
} else if (entity instanceof Event) {
// global window events, or image events
var target = entity.currentTarget;
display = target;
} else {
// not sure if there are others
}
capture(entity);
console.log('[onanyerror]', display, entity);
}
/**
* Capture stuff for debugging purposes.
*
* Keep them in memory so you can reference them
* in the chrome debugger as `onanyerror0` up to `onanyerror99`.
*/
function capture(entity) {
captures.push(entity);
if (captures.length > 100) captures.unshift();
// keep the last ones around
var i = captures.length;
while (--i) {
var x = captures[i];
window['onanyerror' + i] = x;
}
}
/**
* Wait til next code execution cycle as fast as possible.
*/
function onnext(fn) {
setTimeout(fn, 0);
}
})();