You can use the Error.argumentNull
method to generate an exception of that type by passing the name of the missing parameter
and a description as shown here:
Error.argumentNull("x", "The x parameter was not provided.");
Also, suppose you had implemented the classic try/catch block in your JavaScript,
and checking for a necessary condition turned out to be false. You can generate a custom
typed exception for proper handling later. The create method is all that is needed to create
a custom exception as shown in the following GenerateError function:
function GenerateError() {
try
CHAPTER 4 ?– ASP.NET AJAX CLIENT LIBRARIES 60
{
throw Error.create('A custom error was generated');
}
catch(e)
{
alert(e.message);
}
}
Running the function displays the error message to the user as shown in Figure 4-3.
Figure 4-3. Displaying a custom generated error
Consequently, if you needed to have additional properties in the custom exception,
you provide another object to the create method, which contains a list of key/value pairs
to the create method such as those illustrated in the following script:
var errParms = {source: 'GenerateError', ErrorID: '999'};
Error.
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