Error Handling Demo

JavaScript FAQ | Error Handling  

Question: Can I dynamically change the JavaScript error handler?

Answer: Yes. To change the JavaScript error handler, just set window.onerror to the name of the function that will serve as your new error handler.

Here's a demo that lets you test three different error handlers:

  • the browser's default error handler
  • an error handler that displays a customized alert box
  • a "silent" error handler that suppresses all error messages.
    1. Use the select box to set or change the error handler.
    2. Click Fire an Error to test the active error handler.

    Below is the source code of the error handling functions used in this demo:

    function defaultHandler() {return false}
    function silentHandler()  {return true}
    function customHandler(desc,page,line,chr)  {
      'JavaScript error occurred! \n'
     +'The error was handled by '
     +'a customized error handler.\n'
     +'\nError description: \t'+desc
     +'\nPage address:      \t'+page
     +'\nLine number:       \t'+line
     return true
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