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Applies only to Web Apps

Handle JavaScript Errors

You can handle the JavaScript errors occurring in the following specific situations:

  • During the Ajax refresh of an unescaped Expression with '<script>' tags
  • During the execution of the RunJavaScript action of the HTTPRequestHandler extension

To handle these types of errors you need to define a JavaScript function that will handle the errors and register it as an error handler function.

How to Define a JavaScript Function to Handle the Error

By default, OutSystems provides you with a basic error handler function called OsAlertExceptionHandler , which displays an alert box with information about the error.

You can use the OsAlertExceptionHandler function to handle the JavaScript errors or you can define your own function with the following signature:

function <ErrorHandlerFunctionName>( event, exception [, errorCode] [, origin] )

The arguments are:

  • event: jQuery event.
  • exception: JavaScript exception instance that raised the error. For more details about the error use the and exception.message properties.
  • errorCode: Integer that identifies the type of the error (optional argument).
  • origin: JavaScript function where the error was trapped (optional argument).

The following error codes are predefined and you can use them in the logic of your function:

  • outsystems.osErrorCodes.UserJavascriptError: Occurs during the execution of the RunJavaScript action of the HTTPRequestHandler extension in an Action Flow or during an Ajax refresh of an unescaped expression with '<script>' tags.
  • outsystems.osErrorCodes.ConnectionError: This is a connection error and can occur at the beginning or during an Ajax request to the server.
  • outsystems.osErrorCodes.SystemJavascriptError: Occurs when an unexpected exception is raised while executing an OutSystems' Ajax JavaScript.

How to Register the Error Handler Function

To set your JavaScript function for error handling you must register it. For that, add the following JavaScript code to your Module:


If you want to use OutSystems OsAlertExceptionHandler function, you must register it.

The example below shows the definition, in the scope of the Module, of a function to handle the JavaScript errors and its registration as an error handler function:

You may register multiple functions to handle errors. All the registered error handler functions are executed when a JavaScript error occurs.

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