Slide 15.23: JavaScript throw statement

JavaScript 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. The exception can be a string, integer, Boolean or an object.

The example determines the value of a variable called x. A proper error message is displayed if the value of x is

lower than or equal to 0,
not a number, or
not an integer.

If the value is a real number, only the integer part is extracted.

The isNaN function evaluates an argument to determine if it is not a number. It is a top-level function and is not associated with any object.

The method split([separator][, limit]) of the object String splits a string into an array of strings by separating the string into substrings where
- separator specifies the character for separating the string, and
- limit specifies a limit on the number of splits to be found.

Demonstration
The following demonstration shows how the script of HTML and JavaScript is displayed on the Web.


<html> <head> <script type="text/javascript"> function myprog( ) { var a = 10; var b = 0; try { if ( b == 0 ) throw( "Divide by zero error." ); else var c = a / b; } catch ( e ) { alert( "Error: " + e ); } } </script> </head> <body> <form> <input type="button" value="Click Me" onclick="myprog( );" /> </form> </body> </html>