AJAX - The Complete Reference

PART II

Chapter 6: Networking Considerations 267

this value, it is necessary to ensure that all related script and link references are modified as

well. These may even be located in other files, including libraries, so be careful.

Changing class values is not quite as dangerous, since experience shows that most

JavaScript developers tend not to manipulate class values as often as they do id values.

However, class name reduction ultimately suffers from the same problem as id reduction,

so again, be careful.

NNOT EOTE You might be tempted to remap name attributes, particularly on form fields, since these

values are also operated on by server-side programs that would have to be altered as well. This

would of course impact the application architecture more than some other optimizations, so

proceed with caution.

JavaScript Optimizations

Given Ajax’s intrinsic use of JavaScript, often lots of it, you might need to really concentrate

on reducing your script footprint. Many of the techniques for JavaScript optimization are

similar to those used for markup and CSS. However, JavaScript optimization must be

performed far more carefully because, if it is done improperly, the result is not just a visual

distortion, but potentially a broken page! Let’s start with the most obvious and easiest

improvements and then move on to ones that require greater care.

1. Remove JavaScript comments.
   Except for the masking comment, all JavaScript comments indicated
   by // or / / can safely be removed, as they offer no value to end users (except
   for the ones who want to understand how your script works). The comment
   removal may make the script less of a teacher both to those who want to learn
   legitimately and those who want to figure out an exploit.


2. Remove whitespace in JavaScript.
   Interestingly, whitespace removal in JavaScript is not nearly as beneficial as it might
   seem. Certainly code like:

x = x + 1;

can obviously be reduced to:

x=x+1;

However, because of the common sloppy coding practice of JavaScript developers

failing to terminate lines with semicolons, whitespace reduction can cause problems.

For example, given the following legal JavaScript below, which uses implied

semicolons:

x=x+1

y=y+1

a simple whitespace remover tool might produce:

x=x+1y=y+1

which would obviously throw an error. By adding in the needed semicolons to

produce:

x=x+1;y=y+1