Jscript 5.0唯一的改变是引入了错误处理。
Java风格的try和catch结构在Jscript 5.0中得到了支持。例如：
Function GetSomeKindOfIndexThingy() {
Try {
// If an exception occurs during the execution of this
// block of code, processing of this entire block will
// be aborted and will resume with the first statement in its
// associated catch block.
Var objSomething = Server.CreateObject (“SomeComponent”);
Var intIndex = objSomething.getSomeIndex();
Return intIndex;
}
catch (exception) {
// This code will execute when *any* exception occurs during the
// execution of this function
alert (‘Oh dear, the object didn’t expect you to do that’);
}
}
内建的Jscript Error对象有3个属性，它们定义了上次的运行期错误。可在catch块中使用它们获得有关错误的更多信息。
Alert (Error.number); // Gives the numeric value of the error number
// And the result with 0xFFFF to get a ‘normal’ error number in ASP
Alert (error.description); // Gives an error desciption as a string
假如你想招抛出自己的错误，可用一个定制的异常对象引发一个错误（或异常）。然而，由于没有内建的异常对象，必须自己定义一个结构：
// Define our own Exception object
function MyException (intNumber, strDescripton, strInfo) {
this.Number = intNumber; // Set the Number property
this.Description = strDescription; // Set the Description property
this.CustomInfo = strInfo; // Set some ‘information’ property
}
这样的对象可用来在页面中引发定制的异常。这通过使用throw关键字，然后检查catch块中的异常类型来实现：
function GetSomeKindOfIndexThingy() {
try {
Var objSomething = Server.CreateObject (“SomeComponent”);
Var intIndex = objSomething.getSomeIndex();
If (intIndex == 0) {
// Create a new MyException object
theException = new MyException (0x6F1, “Zero index not permitted”,
“Index_Err”);
throw theException;
}
catch (objException) {
if (objException instanceof MyException) {
// This is one of our custom exption objects
if (objException.Category == “Index_Err”) {
alert (‘Index Error: ‘ + objException.Description);
else
alert (‘Undefined custom error: ‘ + objException.Description);
}
else
// Not “our” exception, so display it and raise to next higher routine
alert (Error.Description + ‘ (‘ + Error.Number + ‘)’);
throw exception;
}
}
}