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JavaScript Throw Statement
The throw statement allows you to create an exception.
The Throw Statement
The throw statement allows you to create an exception. If you use this statement together with the try...catch statement, you can control program flow and generate accurate error messages.
Syntax
throw exception
The exception can be a string, integer, Boolean or an object.
Note that throw is written in lowercase letters. Using uppercase letters will generate a JavaScript error!
Example
The example below determines the value of a variable called x. If the value of x is higher than 10, lower than 0, or not a number, we are going to throw an error. The error is then caught by the catch argument and the proper error message is displayed:
Example
<html>
<body>
<script type="text/javascript">
var x=prompt("Enter a number between 5 and 10:","");
try
{
if(x>10)
{
throw "Err1";
}
else if(x<5)
{
throw "Err2";
}
else if(isNaN(x))
{
throw "Err3";
}
}
catch(err)
{
if(err=="Err1")
{
document.write("Error! The value is too high.");
}
if(err=="Err2")
{
document.write("Error! The value is too low.");
}
if(err=="Err3")
{
document.write("Error! The value is not a number.");
}
}
</script>
</body>
</html>
<body>
<script type="text/javascript">
var x=prompt("Enter a number between 5 and 10:","");
try
{
if(x>10)
{
throw "Err1";
}
else if(x<5)
{
throw "Err2";
}
else if(isNaN(x))
{
throw "Err3";
}
}
catch(err)
{
if(err=="Err1")
{
document.write("Error! The value is too high.");
}
if(err=="Err2")
{
document.write("Error! The value is too low.");
}
if(err=="Err3")
{
document.write("Error! The value is not a number.");
}
}
</script>
</body>
</html>
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W3Schools is optimized for learning, testing, and training. Examples might be simplified to improve reading and basic understanding.
Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content.
While using this site, you agree to have read and accepted our terms of use and privacy policy.
Copyright 1999-2012 by Refsnes Data. All Rights Reserved.
Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content.
While using this site, you agree to have read and accepted our terms of use and privacy policy.
Copyright 1999-2012 by Refsnes Data. All Rights Reserved.