| 3. 13. 1. try...catch |
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Syntax |
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try{
statement1
}catch(exception){
statement2
}
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It can be used to handle all or some of the errors that can occur in a script. |
If an error is not handled by a try...catch statement, it is passed on so other statements can handle the error. |
If there are no other statements to handle the error, it is passed to the browser to handle. |
statement1 is where an error can occur, while statement2 is used to handle the error. |
As soon as an error occurs, the value thrown is passed to the catch portion of the statement and stored in exception. |
If the error can not be handled, another throw statement is used to pass the error to a higher level handler if one is defined. |
It is possible to have nested try...catch statements within try...catch statements. |
The following example uses a try...catch Statement to Handle an Incorrect Entry. |
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<html>
<head>
<title>Using a try..catch statement</title>
<script language="JavaScript">
<!--
function myErrorHandler(data){
try{
try{
if(data == "string"){
throw "E0";
}else{
throw "E1";
}
}catch(e){
if(e == "E0"){
return("Error (" + e + "): Entry must be numeric.");
}else{
throw e;
}
}
}catch (e){
return("Error (" + e + "): Entry was invalid.");
}
}
function processData(form){
if(isNaN(parseInt(form.myText.value))){
alert(myErrorHandler("string"));
}else{
alert("You have correctly entered a number");
}
}
-->
</script>
</head>
<body>
<form name="myForm">
Please enter a number:
<input type=TEXT size=10 value="" name="myText">
<input type=BUTTON value="Process" name="myButton" onClick='processData(this.form)'>
</form>
</body>
</html>
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