| Re: including CSS & JS on only pages that need that CSS & JS [message #175597 is a reply to message #175579] |
Mon, 10 October 2011 21:17   |
Thomas 'PointedEars'
Messages: 701
Registered: October 2010
Karma:
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Senior Member |
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Mr. B-o-B wrote:
> On 10/9/2011 6:54 PM, Jerry Stuckle cried from the depths of the abyss:
>> And files should be included using link tags, not directly included in
>> the source file directly (unless they are specific to this page - in
>> which case there is no need for conditional includes). That way file can
>> be cached by the browser and/or routers between the web server and the
>> client, decreasing both network traffic and server load.
>
> Again, my original post fits these specs:
>
> if (@isset $jerrys_css) {
> echo "<link rel=\"stylesheet\" type=\"text/css\" href=\"jerry_css.css\"
> />";
> }
>
> Then just set $jerry_css = 1 when needed. Imagine that. You are not
> decreasing network traffic, not increasing server load, cache is
> irrelevant as it's only cached in the pages that need it, you are using
> .js/.css via link tags.
This looks increasingly like blind teaching the blind. As the subject is in
fact partially on-topic here, since PHP can be used server-side:
0. Routers do not cache HTTP requests. They usually work on lower levels
of the TCP/IP stack, the Transport (TCP) and Internet Layer (IP), and
usually see only TCP and IP packets. Not only is a HTTP message usually
split into several IP packets, but also is the payload transported by
such a packet reduced so that the packet size does not exceed the MTU of
the link, considering the header information of the packet as well.
So we can safely dismiss the suggestion that the composition of Web
resources could affect packet caching, if that even happens (routers
usually cache *routing information*), as completely b…ogus.
1. You cannot "use .js via link tags". Client-side scripts have to be
included using `script' elements.
It is the best current practice that all client-side scripts required
for a document be included with one request, unless it is feasible and
more efficient to load some of them dynamically when needed. Which
usually means that the request triggers a server-side script that
composes the response for that one script.
2. It makes no difference to the number of requests whether you include
other stylesheets with the CSS @import rule or the (X)HTML `link'
element. Cacheability is equal, too, as with the CSS directive the
source code does not change as well. [The same applies for scripts
being loaded dynamically.]
The main difference is in compatibility. Rather ancient user agents
would not support the `@import' rule but would support the `link'
element:
<http://w3development.de/css/hide_css_from_browsers/import/>
[Much the same applies for dynamic script loading. It usually requires
XHR support or sufficient DOM support, while the plain `script' element
is more compatible and reliable.]
3. It does make a difference to the loading speed of a Web site and the
network traffic caused by it if you create one response from content of
several CSS resources, as that is only one request. Doing so is the best
current practice. As for caching, it rarely makes sense to exclude CSS
rules from the generated response even if they are not used.
It really is a matter of loading speed/traffic vs. cacheability; usually,
loading speed is considered to be more important, as local caches are
usually large enough to handle the differences and visitors do not like
to wait.
4. Requests for client-side scripts should be caused last, at least after
the requests for stylesheets:
<http://code.google.com/speed/page-
speed/docs/rtt.html#PutStylesBeforeScripts>
Bottom line: Fewer requests and smaller responses are better.
I have started writing a general resource builder in PHP to do that. So far
it works without problems for client-side scripts even in a production
environment:
< http://PointedEars.de/websvn/filedetails.php?repname=JSX&path=%2Ftrunk% 2Fbuilder.php>
(The ultimate goal is that it resolves dependencies of resources
automatically.)
Constructive comments are welcome.
PointedEars
--
Use any version of Microsoft Frontpage to create your site.
(This won't prevent people from viewing your source, but no one
will want to steal it.)
-- from <http://www.vortex-webdesign.com/help/hidesource.htm> (404-comp.)
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