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 Player 7

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."; }

In a FLA or AS file, enter the following ActionScript in Frame 1 of the Timeline:

import InvalidEmailAddress; 
function checkEmail(email:String) { 
 if (email.indexOf("@") == -1) { 
 throw new InvalidEmailAddress(); 
 } 
} 
try { 
 checkEmail("Joe Smith"); 
} 
catch (e) { 
 this.createTextField("error_txt", this.getNextHighestDepth(), 0, 0, 100, 22); 
 error_txt.autoSize = true; 
 error_txt.text = e.toString(); 
}

throw statement

Parameters

Example

See also