HTML and CSS Reference
In-Depth Information
Figure 7.21 An error was caught and its name and the reason for it are displayed.
The throw Statement. The throw statement allows you to create your own condi-
tions for exceptions. Used within in the try block, a specific error condition can be tested
and thrown to the catch block. In the catch block you can create customized error mes-
sages to correspond to a particular error. See Example 7.13.
The finally Clause. You can use the finally clause to execute statements after the try
statement finishes, whether or not an exception occurred.
You can use the finally clause to make your script fail gracefully when an exception
occurs; for example, you might need to release a resource that your script has tied up.
The following example opens a file and then executes statements that use the file
(server-side JavaScript allows you to access files). If an exception is thrown while the file
is open, the finally clause closes the file before the script fails.
<head><title>Catch me if you Can!</title></head>
<script type="text/javascript">
var age=eval(prompt("Enter your age:",""));
try {
if(age>120 || age < 0){
throw "Error1" ;
else if(age == ""){
throw "Error2 ";
else if(isNaN(age)){
throw "Error3 ";
catch(err) {
if(err=="Error1") {
alert("Error! The value is out of range");
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