Web development platforms like JSP, ASP.NET, ColdFusion, and
so forth offer plenty of powerful development options on the server side.
while offloading processing from the server. While it has been with us for many
years, development tools are still a bit awkward. Let’s take a closer look at
If you are accustomed to working with development IDEs like Visual Studio or NetBeans, then you are familiar
with the various debugging options, which include stepping through code,
setting breakpoints, and watching variables. These are invaluable tools when
monitoring code execution or tracking down a bug. Unfortunately, these tools
A critical step in application development is tracking down
bugs in a script or code. This involves isolating code chunks and analyzing
methods used before the advancement of development tools.
the alert message box. You can use it to inspect values stored in variables/objects and combine with a loop to view the contents of an object.
As an example, the HTML in
Listing A is not executing as planned. Basically, it verifies
values that are entered in two text fields before the form is actually
The form is always submitted regardless of values entered,
so we can use alert statements to inspect the contents of values during script
execution. The script in
uses alert statements to monitor variable values.
If you execute the script, it is clear the
if statements always evaluate to true. Upon closer inspection, you will
notice the assignment operation is being used (=) as opposed to equality (==).
By making these two changes, the script will execute as expected.
This error is common, especially when developers are moving
back-and-forth between languages like VB.NET and others that have different
syntax. Here’s a quick look at more common errors:
utilize proper formatting/case. Use a consistent naming convention for
your objects, variables, and function names.
separator character for arguments.
uses curly braces to define a block of statements.
must be enclosed in quotes (single or double).
developers, but these days there are other options for monitoring a script,
including browser tools and IDEs.
While Internet Explorer is the most popular browser, its
leave much to be desired, but they do let you know which errors occur. The
messages include a line number (even though it never corresponds to the actual
offending line, it does place you in the vicinity).
Also, it can launch an external application for debugging
Mozilla-based browsers provide
console that displays messages (errors, warnings, information) about scripts on
the current page. It actually displays the offending code with an arrow
pointing to where the error occurred.
browsers include special syntax for debugging. A good example is Opera, which
supports the opera.postError() command to send output to the console. The Safari browser
will appear in its console.
You may be able to debug browser-based applications via your
favorite IDE. Visual Studio is one example that allows you to debug Internet
Explorer applications via its debugging support. You must have debugging
enabled on the Web server (IIS). Follow these steps to use it:
the Web application in debug mode (Debug | Start).
application launches in a browser window. Return to the Visual Studio
client. Select Debug | Window | Running Documents.
currently running application will appear in the Running Documents window.
You can select the Web form and actually place breakpoints in the
to the Web form and use the application; execution will halt at any
Visual Studio is not alone with its debug support. For
debug syntax and logic errors, as well as setting breakpoints, watching
variables, and stepping through code. A nice feature is the inclusion of an
HTML Debugger, which is a full-featured development tool. If you utilize
the Eclipse IDE, JSEclipse
Another language to debug
scripting. It has an overwhelming number of language resources, but development
tend to utilize older approaches to debugging, but there are many tools
available today to ease the testing and debugger load.
Tony Patton began his professional career as an application developer earning Java, VB, Lotus, and XML certifications to bolster his knowledge.
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