Windows.onerror

This error object will contain our coveted stack property in every modern browser. Consider the following helper method, invoke , which calls a function on an object with an array of arguments:. Of course, doing this manually everywhere is pretty cumbersome. You can make it easier by creating a generic wrapper utility function:. Because JavaScript is single threaded, you don't need to use wrap everywhere — just at the beginning of every new stack.

If that seems like a heck of a lot of work, don't worry! Most error reporting libraries have mechanisms for augmenting built-in functions like addEventListener and setTimeout so that you don't have to call a wrapping utility every time yourself. And, yes, raven-js does this too. Okay, so you've done your job — you've plugged into window. There's just one last step: transmitting the error information to your servers. Note that if you have to transmit your error across different origins, your reporting endpoint will need to support CORS Cross Origin Resource Sharing.

Psst, you might want to try Sentry to debug JavaScript. Archive Twitter Feed. Share on Twitter. Share on Facebook. Share on HackerNews. January 4, Error: foobar at bar Unknown script code at foo Unknown script code at Anonymous function Unknown script code at Anonymous function Unknown script code at Anonymous function Unknown script code ReferenceError message : ex.

Your code is broken. Checking Err after each interaction with an object removes ambiguity about which object was accessed by the code. You can be sure which object placed the error code in Err. Number , as well as which object originally generated the error the object specified in Err.

On Error GoTo 0 disables error handling in the current procedure. It doesn't specify line 0 as the start of the error-handling code, even if the procedure contains a line numbered 0. Without an On Error GoTo 0 statement, an error handler is automatically disabled when a procedure is exited. On Error GoTo -1 disables the exception in the current procedure.

It does not specify line -1 as the start of the error-handling code, even if the procedure contains a line numbered Without an On Error GoTo -1 statement, an exception is automatically disabled when a procedure is exited. To prevent error-handling code from running when no error has occurred, place an Exit Sub , Exit Function , or Exit Property statement immediately before the error-handling routine, as in the following fragment:.

Here, the error-handling code follows the Exit Sub statement and precedes the End Sub statement to separate it from the procedure flow. You can place error-handling code anywhere in a procedure. Untrapped errors in objects are returned to the controlling application when the object is running as an executable file. Within the development environment, untrapped errors are returned to the controlling application only if the proper options are set. See your host application's documentation for a description of which options should be set during debugging, how to set them, and whether the host can create classes.

If you create an object that accesses other objects, you should try to handle any unhandled errors they pass back. If you cannot, map the error codes in Err. Number to one of your own errors and then pass them back to the caller of your object. You should specify your error by adding your error code to the VbObjectError constant.

For example, if your error code is , assign it as follows:. System errors during calls to Windows dynamic-link libraries DLLs do not raise exceptions and cannot be trapped with Visual Basic error trapping.

Error events are fired at various targets for different kinds of errors: When a JavaScript runtime error including syntax errors and exceptions thrown within handlers occurs, an error event using interface ErrorEvent is fired at window and window.

These error events do not bubble up to window, but can be handled with a EventTarget. Capture and report JavaScript errors with window.