The try&catch Statement

The try...catch statement allows you to test a block of code for errors. The try block contains the code to be run, and the catch block contains the code to be executed if an error occurs. Syntax:

try
{
//Run some code here
}
catch(err)
{
//Handle errors here
}

Note that try...catch is written in lowercase letters. Using uppercase letters will generate a JavaScript error!

Examples

The example below is supposed to alert "Welcome guest!" when the button is clicked. However, there's a typo in the message() function. alert() is misspelled as adddlert(). A JavaScript error occurs. The catch block catches the error and executes a custom code to handle it. The code displays a custom error message informing the user what happened:

try
{
adddlert("Welcome guest!");
}
catch(err)
{
txt="There was an error on this page.\n\n";
txt+="Error description: " + err.description + "\n\n";
txt+="Click OK to continue.\n\n";
alert(txt);
}