User Guide

216 ActionScript language elements
See also
=== strict equality operator
throw statement
throw expression
Generates, or throws, an error that can be handled, or caught, by a catch{} code block. If an
exception is not caught by a
catch block, the string representation of the thrown value is sent
to the Output panel.
Typically, you throw instances of the Error class or its subclasses (see the Example section).
Availability: ActionScript 1.0; Flash Lite 2.0
Parameters
expression:Object - An ActionScript expression or object.
Example
In this example, a function named checkEmail() checks whether the string that is passed to
it is a properly formatted e-mail address. If the string does not contain an @ symbol, the
function throws an error.
function checkEmail(email:String) {
if (email.indexOf("@") == -1) {
throw new Error("Invalid email address");
}
}
checkEmail("someuser_theirdomain.com");
The following code then calls the checkEmail() function within a try code block. If the
email_txtstring does not contain a valid e-mail address, the error message appears in a text
field (
error_txt).
try {
checkEmail("Joe Smith");
}
catch (e) {
error_txt.text = e.toString();
}
In the following example, a subclass of the Error class is thrown. The checkEmail() function
is modified to throw an instance of that subclass.
// Define Error subclass InvalidEmailError // In InvalidEmailError.as:
class InvalidEmailAddress extends Error { var message = "Invalid email
address."; }