Logo         Community
  Trog
Services
The Company
Community
Columns
Your Account
Contact Us
 
 
JavaScript Exception Handling
Use the JavaScript Error object to trap and resolve errors in script execution.

| Playing Catch |

So that's what an error looks like. And now that you've seen what makes it tick, how about writing something to handle it?

JavaScript allows you to trap errors using the standard "try-catch" exception-handling combination. Here's what it looks like:


try {
execute this block
} catch (error) {
execute this block if error
}


Take a look at this rewrite of the previous example, which incorporates a simple exception handler.


<script language="JavaScript">

try {
colours[2] = "red";
} catch (e) {
alert("Oops! Something bad just happened. Calling 911...");
}

</script>


And this time, when the script is executed, it will not generate an error - instead, it will output

''.preg_replace(array('/  /', '/ /'), array('  ', '   '), '
Oops! Something bad just happened. Calling 911...
').'
'

This is a very basic example of how JavaScript exceptions can be trapped, and appropriate action triggered. As you will see, the ability to handle errors in a transparent manner throws open some pretty powerful possibilities...but more on that later.

The first part of the code introduces you to the "try" block; this instructs JavaScript to try - literally - to execute the statements within the enclosing block.


try {
colours[2] = "red";
}


The "catch" block sets up the exception handler, in the event that one is generated. This does the hard work of trapping the exception and suggesting how to handle it.


catch (e) {
alert("Oops! Something bad just happened. Calling 911...");
}


If an exception is generated, the "catch" segment of the code will be triggered, and JavaScript's default error handling mechanism will be overridden by the instructions in that code segment - in this case, displaying the text "Something bad happened".


How to do Everything with PHP & MySQL
How to do Everything with PHP & MySQL, the best-selling book by Melonfire, explains how to take full advantage of PHP's built-in support for MySQL and link the results of database queries to Web pages. You'll get full details on PHP programming and MySQL database development, and then you'll learn to use these two cutting-edge technologies together. Easy-to-follow sample applications include a PHP online shopping cart, a MySQL order tracking system, and a PHP/MySQL news publishing system.

Read more, or grab your copy now!


previous page more like this  print this article  next page
 
Search...
 
In trog...
Logging With PHP
Building A Quick-And-Dirty PHP/MySQL Publishing System
Output Buffering With PHP
Date/Time Processing With PHP
Creating Web Calendars With The PEAR Calendar Class
more...
 
In the hitg report...
Crime Scenes
Animal Attraction
Lord Of The Strings
more...
 
In boombox...
Patience - George Michael
Think Tank - Blur
My Private Nation - Train
more...
 
In colophon...
Hostage - Robert Crais
The Dead Heart - Douglas Kennedy
Right As Rain - George Pelecanos
more...
 
In cut!...
American Chai
The Core
Possession
more...
 
Find out how you can use this article on your own Web site!


Copyright © 1998-2018 Melonfire. All rights reserved
Terms and Conditions | Feedback