javascript

Chapter 20: Best Practices
This line tells mod_gzip to compress any file ending with .js that is requested from the browser.
Assuming that all of your JavaScript files end with .js , this will compress every request and apply the
appropriate headers to indicate that the contents have been compressed. For more information about
mod_gzip , visit the project site at http://www.sourceforge.net/projects/mod - gzip/ .
For mod_deflate , you can similarly include a single line to ensure that the JavaScript files are
compressed before being sent. Place the following line in either your httpd.conf file or a
.htaccess file:
#Tell mod_deflate to include all JavaScript files
AddOutputFilterByType DEFLATE application/x-javascript
Note that this line uses the MIME type of the response to determine whether or not to compress it.
Remember that even though text/javascript is used for the type attribute of < script > , JavaScript
files are typically served with a MIME type of application/x - javascript . For more information on
mod_deflate , visit http://httpd.apache.org/docs/2.0/mod/mod_deflate.html .
Both mod_gzip and mod_deflate result in savings of around 70% of the original file size of JavaScript
files. This is largely due to the fact that JavaScript files are plain text and can therefore be compressed
very efficiently. Decreasing the wire weight of your files decreases the amount of time it takes to transmit
to the browser. Keep in mind that there is a slight trade - off, because the server must spend time
compressing the files on each request, and the browser must take some time to decompress the files once
they arrive. Generally speaking, however, the trade - off is well worth it.
Most web servers, both open source and commercial, have some HTTP compression
capabilities. Please consult the documentation for your server to determine how to
configure compression properly.
Summary
As JavaScript development has matured, best practices have emerged. What once was considered a
hobby is now a legitimate profession and, as such, has experienced the type of research into
maintainability, performance, and deployment traditionally done for other programming languages.
Maintainability in JavaScript has to do partially with the following code conventions:
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Code conventions from other languages may be used to determine when to comment and how
to indent, but JavaScript requires some special conventions to make up for the loosely typed
nature of the language.
Since JavaScript must coexist with HTML and CSS, it ’ s also important to let each wholly define
its purpose: JavaScript should define behavior, HTML should define content, and CSS should
define appearance.
Any mixing of these responsibilities can lead to difficult - to - debug errors and maintenance
issues.
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