FEO onerror.js

const { onerror } = window; // Existing onerror handlers

// Trust others adhere to onerror handling rules
window.onerror = (...args) => {
	let handled; // is someone else taking care this error?
	try {
		handled = onerror && onerror.apply(window, args);
	} catch (error) {

		// Catch others' onerror errors
		myOnErrorHandler(error.message, '', 0, 0, error);
	} finally {
		handled || myOnErrorHandler(...args);
	}
	return false;
}

// Or simply be first and catch everything
window.onerror = (...args) => {
	myOnErrorHandler(...args);
	onerror && onerror.apply(window, args);
	return false;
}